v3.26.3
Condensed Consolidated Schedules of Investments (Unaudited) - BXINFRA Aggregator (CYM) L.P - USD ($)
Sep. 30, 2026
Dec. 31, 2025
Summary of Investment Holdings [Line Items]    
Fair Value $ 6,421,142,000 $ 3,555,635,000
Fair Value as a Percentage of Net Assets 101.60% 102.00%
BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Derivative Asset, Fair Value $ 12,204,000 $ 143,000
Derivative Liability, Fair Value 180,000 265,000
BXINFRA Aggregator (CYM) L.P. | Open Swap Contract, Identifier [Axis]: Derivative Assets at Fair Value | Foreign Currency Swaps | Derivative at Fair Value    
Summary of Investment Holdings [Line Items]    
Derivative Asset, Fair Value $ 7,879,000  
Derivative Asset, Fair Value as a Percentage of Net Assets 0.10%  
BXINFRA Aggregator (CYM) L.P. | Open Swap Contract, Identifier [Axis]: Derivative Assets at Fair Value | Interest Rate Swap | Derivative at Fair Value    
Summary of Investment Holdings [Line Items]    
Derivative Asset, Fair Value $ 2,767,000  
Derivative Asset, Fair Value as a Percentage of Net Assets 0.00%  
BXINFRA Aggregator (CYM) L.P. | Open Forward Foreign Currency Contract, Identifier [Axis]: BXINFRA Aggregator (CYM) L.P. | Derivative at Fair Value | Derivative Liabilities at Fair Value | Foreign Currency Contracts    
Summary of Investment Holdings [Line Items]    
Derivative Liability, Fair Value   $ 265,000
Derivative Liability, Fair Value as a Percentage of Net Assets   0.00%
BXINFRA Aggregator (CYM) L.P. | Open Forward Foreign Currency Contract, Identifier [Axis]: Derivative Assets at Fair Value | Foreign Currency Contracts | Derivative at Fair Value    
Summary of Investment Holdings [Line Items]    
Derivative Asset, Fair Value   $ 143,000
Derivative Asset, Fair Value as a Percentage of Net Assets   0.00%
BXINFRA Aggregator (CYM) L.P. | Open Forward Foreign Currency Contract, Identifier [Axis]: Derivative Liabilities at Fair Value | Foreign Currency Contracts | Derivative at Fair Value    
Summary of Investment Holdings [Line Items]    
Derivative Liability, Fair Value $ 180,000  
Derivative Liability, Fair Value as a Percentage of Net Assets 0.00%  
BXINFRA Aggregator (CYM) L.P. | Derivative Assets at Fair Value    
Summary of Investment Holdings [Line Items]    
Derivative Asset, Fair Value $ 12,204,000 $ 143,000
Derivative Asset, Fair Value as a Percentage of Net Assets 0.20% 0.00%
BXINFRA Aggregator (CYM) L.P. | Total Derivatives    
Summary of Investment Holdings [Line Items]    
Derivative, Fair Value $ 12,024,000 $ (122,000)
Derivative, Fair Value as a Percentage of Net Assets 0.20% 0.00%
BXINFRA Aggregator (CYM) L.P. | Derivative Liabilities at Fair Value    
Summary of Investment Holdings [Line Items]    
Derivative Liability, Fair Value $ 180,000 $ 265,000
Derivative Liability, Fair Value as a Percentage of Net Assets 0.00% 0.00%
BXINFRA Aggregator (CYM) L.P. | Open Futures Contract, Identifier [Axis]: Derivative Assets at Fair Value | Bond Futures Contracts | Derivative at Fair Value    
Summary of Investment Holdings [Line Items]    
Derivative Asset, Fair Value $ 1,558,000  
Derivative Asset, Fair Value as a Percentage of Net Assets 0.00%  
BXINFRA Aggregator (CYM) L.P. | Equity Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 5,648,816,000 $ 2,993,177,000 [2]
Fair Value as a Percentage of Net Assets [1] 83.50% 78.40% [2]
BXINFRA Aggregator (CYM) L.P. | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 1,420,735,000 $ 1,166,894,000 [4]
Fair Value as a Percentage of Net Assets [3] 21.00% 30.60% [4]
BXINFRA Aggregator (CYM) L.P. | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value $ 951,667,000 $ 698,531,000 [3]
Fair Value as a Percentage of Net Assets 14.10% 18.30% [3]
BXINFRA Aggregator (CYM) L.P. | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 469,068,000 $ 468,363,000 [4]
Fair Value as a Percentage of Net Assets [3] 6.90% 12.30% [4]
BXINFRA Aggregator (CYM) L.P. | Investment    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 7,069,551,000 $ 4,160,071,000 [4]
Fair Value as a Percentage of Net Assets [3] 104.50% 109.00% [4]
BXINFRA Aggregator (CYM) L.P. | Money Market Fund    
Summary of Investment Holdings [Line Items]    
Money Market Fund, Fair Value $ 15,223,000 $ 13,482,000
Money Market Fund, Fair Value as a Percentage of Net Assets 0.20% 0.40%
BXINFRA Aggregator (CYM) L.P. | Cash    
Summary of Investment Holdings [Line Items]    
Money Market Fund, Fair Value $ 97,599,000 $ 51,262,000
Money Market Fund, Fair Value as a Percentage of Net Assets 1.40% 1.30%
BXINFRA Aggregator (CYM) L.P. | Cash and Cash Equivalents    
Summary of Investment Holdings [Line Items]    
Money Market Fund, Fair Value $ 112,822,000 $ 64,744,000
Money Market Fund, Fair Value as a Percentage of Net Assets 1.70% 1.70%
BXINFRA Aggregator (CYM) L.P. | Total Investments, Investments in Affiliated Investee Funds, Cash and Cash Equivalents and Derivative Instruments    
Summary of Investment Holdings [Line Items]    
Total Investments, Investments in Affiliated Investee Funds, Cash and Cash Equivalents and Derivative Instruments, Fair Value $ 7,194,397,000 $ 4,224,693,000
Total Investments, Investments in Affiliated Investee Funds, Cash and Cash Equivalents and Derivative Instruments, Fair Value as a Percentage of Net Assets 106.30% 110.70%
BXINFRA Aggregator (CYM) L.P. | Digital Infrastructure | Equity Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 1,539,566,000 $ 612,429,000
Fair Value as a Percentage of Net Assets [1] 22.80% 16.00%
BXINFRA Aggregator (CYM) L.P. | Digital Infrastructure | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value $ 102,749,000  
Fair Value as a Percentage of Net Assets 1.50%  
BXINFRA Aggregator (CYM) L.P. | Digital Infrastructure | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 126,725,000
Fair Value as a Percentage of Net Assets [3]   3.30%
BXINFRA Aggregator (CYM) L.P. | Digital Infrastructure | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 3,975,000 $ 2,135,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.10% 0.10% [3]
BXINFRA Aggregator (CYM) L.P. | Energy Infrastructure | Equity Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 201,804,000 $ 123,060,000
Fair Value as a Percentage of Net Assets [1] 3.00% 3.20%
BXINFRA Aggregator (CYM) L.P. | Energy Infrastructure | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value $ 101,622,000  
Fair Value as a Percentage of Net Assets 1.50%  
BXINFRA Aggregator (CYM) L.P. | Energy Infrastructure | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 62,031,000
Fair Value as a Percentage of Net Assets [3]   1.60%
BXINFRA Aggregator (CYM) L.P. | Energy Infrastructure | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 6,086,000 $ 6,408,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.10% 0.20% [3]
BXINFRA Aggregator (CYM) L.P. | Technology, Media and Entertainment | Equity Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 23,088,000  
Fair Value as a Percentage of Net Assets [1] 0.30%  
BXINFRA Aggregator (CYM) L.P. | Technology, Media and Entertainment | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value $ 9,929,000  
Fair Value as a Percentage of Net Assets 0.10%  
BXINFRA Aggregator (CYM) L.P. | Technology, Media and Entertainment | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 20,012,000
Fair Value as a Percentage of Net Assets [3]   0.50%
BXINFRA Aggregator (CYM) L.P. | Technology, Media and Entertainment | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 60,630,000 $ 96,107,000 [4]
Fair Value as a Percentage of Net Assets [3] 0.90% 2.50% [4]
BXINFRA Aggregator (CYM) L.P. | Transportation Infrastructure | Equity Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 1,602,457,000 $ 1,337,209,000
Fair Value as a Percentage of Net Assets [1] 23.70% 35.00%
BXINFRA Aggregator (CYM) L.P. | Transportation Infrastructure | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 148,042,000  
Fair Value as a Percentage of Net Assets [3] 2.20%  
BXINFRA Aggregator (CYM) L.P. | Transportation Infrastructure | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 137,885,000
Fair Value as a Percentage of Net Assets [3]   3.60%
BXINFRA Aggregator (CYM) L.P. | Transportation Infrastructure | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [3],[4]   $ 11,134,000
Fair Value as a Percentage of Net Assets [3],[4]   0.30%
BXINFRA Aggregator (CYM) L.P. | Water & Waste Infrastructure | Equity Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 204,516,000  
Fair Value as a Percentage of Net Assets [1] 3.00%  
BXINFRA Aggregator (CYM) L.P. | Various | Equity Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [1],[2] $ 2,077,385,000 $ 920,479,000
Fair Value as a Percentage of Net Assets [1],[2] 30.70% 24.10%
BXINFRA Aggregator (CYM) L.P. | Various | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [2] $ 12,034,000  
Fair Value as a Percentage of Net Assets 0.20%  
BXINFRA Aggregator (CYM) L.P. | Consumer and Services | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 54,824,000  
Fair Value as a Percentage of Net Assets [3] 0.80%  
BXINFRA Aggregator (CYM) L.P. | Consumer and Services | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 39,408,000
Fair Value as a Percentage of Net Assets [3]   1.00%
BXINFRA Aggregator (CYM) L.P. | Consumer and Services | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 153,601,000 $ 137,265,000 [3]
Fair Value as a Percentage of Net Assets [4] 2.30% 3.60% [3]
BXINFRA Aggregator (CYM) L.P. | Energy | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value $ 176,710,000  
Fair Value as a Percentage of Net Assets 2.60%  
BXINFRA Aggregator (CYM) L.P. | Energy | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 197,485,000
Fair Value as a Percentage of Net Assets [3]   5.20%
BXINFRA Aggregator (CYM) L.P. | Energy | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 7,713,000 $ 4,283,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.10% 0.10% [3]
BXINFRA Aggregator (CYM) L.P. | Industrials | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value $ 11,673,000  
Fair Value as a Percentage of Net Assets 0.20%  
BXINFRA Aggregator (CYM) L.P. | Industrials | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 2,549,000
Fair Value as a Percentage of Net Assets [3]   0.10%
BXINFRA Aggregator (CYM) L.P. | Industrials | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 34,994,000 $ 35,592,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.50% 0.90% [3]
BXINFRA Aggregator (CYM) L.P. | Infrastructure Services | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value $ 122,092,000  
Fair Value as a Percentage of Net Assets 1.80%  
BXINFRA Aggregator (CYM) L.P. | Infrastructure Services | Debt Investments - Infrastructure    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 112,436,000
Fair Value as a Percentage of Net Assets [3]   2.90%
BXINFRA Aggregator (CYM) L.P. | Infrastructure Services | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [3],[4] $ 135,591,000 $ 131,261,000
Fair Value as a Percentage of Net Assets [3],[4] 2.00% 3.40%
BXINFRA Aggregator (CYM) L.P. | Real Estate | Debt Investments    
Summary of Investment Holdings [Line Items]    
Fair Value $ 211,992,000  
Fair Value as a Percentage of Net Assets 3.10%  
BXINFRA Aggregator (CYM) L.P. | Real Estate | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 8,076,000 $ 6,147,000 [4]
Fair Value as a Percentage of Net Assets [3] 0.10% 0.20% [4]
BXINFRA Aggregator (CYM) L.P. | Healthcare | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 41,308,000 $ 38,031,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.60% 1.00% [3]
BXINFRA Aggregator (CYM) L.P. | Transportation Infrastructure | Debt Investments - Liquid    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 17,094,000  
Fair Value as a Percentage of Net Assets [3] 0.30%  
Investment, Identifier [Axis]: Cash | Cash Held at Banks | Cash and Cash Equivalents | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Money Market Fund, Fair Value $ 97,599,000 $ 51,262,000
Money Market Fund, Fair Value as a Percentage of Net Assets 1.40% 1.30%
Investment, Identifier [Axis]: Consumer and Services | Other Investment(s) in Debt 1 | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 41,030,000 $ 29,670,000
Fair Value as a Percentage of Net Assets [3] 0.60% 0.80%
Investment, Identifier [Axis]: Consumer and Services | Other Investment(s) in Debt 1 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 143,861,000 $ 128,251,000 [3]
Fair Value as a Percentage of Net Assets [4] 2.10% 3.40% [3]
Investment, Identifier [Axis]: Consumer and Services | Other Investment(s) in Debt 2 | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 13,794,000 $ 9,738,000
Fair Value as a Percentage of Net Assets [3] 0.20% 0.30%
Investment, Identifier [Axis]: Consumer and Services | Other Investment(s) in Debt 2 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 9,740,000 $ 9,014,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.10% 0.20% [3]
Investment, Identifier [Axis]: Digital Infrastructure | Aspen Holdco III L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 342,128,000  
Fair Value as a Percentage of Net Assets [1] 5.10%  
Investment, Identifier [Axis]: Digital Infrastructure | Eucalyptus I HoldCo (CYM) L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1],[5] $ 489,514,000  
Fair Value as a Percentage of Net Assets [1],[5] 7.20%  
Investment, Identifier [Axis]: Digital Infrastructure | Eucalyptus I HoldCo (CYM) L.P. | Equity Investments| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1]   $ 346,583,000
Fair Value as a Percentage of Net Assets [1]   9.10%
Investment, Identifier [Axis]: Digital Infrastructure | Odyssey Holdco L.L.C. | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 12,207,000 $ 25,001,000 [3]
Fair Value as a Percentage of Net Assets 0.20% 0.70% [3]
Investment, Identifier [Axis]: Digital Infrastructure | Odyssey Holdco L.L.C. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 415,605,000  
Fair Value as a Percentage of Net Assets [1] 6.10%  
Investment, Identifier [Axis]: Digital Infrastructure | Odyssey Holdco L.L.C. | Equity Investments| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1],[5]   $ 244,587,000
Fair Value as a Percentage of Net Assets [1],[5]   6.40%
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 90,542,000 $ 101,724,000 [3]
Fair Value as a Percentage of Net Assets 1.30% 2.70% [3]
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 3,975,000 $ 2,135,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.10% 0.10% [3]
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Equity 1 | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 291,560,000  
Fair Value as a Percentage of Net Assets [1] 4.30%  
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Equity 2 | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 759,000  
Fair Value as a Percentage of Net Assets [1] 0.00%  
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Equity | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1]   $ 21,259,000
Fair Value as a Percentage of Net Assets [1]   0.60%
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 101,622,000 $ 62,031,000 [3]
Fair Value as a Percentage of Net Assets 1.50% 1.60% [3]
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 6,086,000 $ 6,408,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.10% 0.20% [3]
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Equity 1 | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 148,431,000  
Fair Value as a Percentage of Net Assets [1] 2.20%  
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Equity 2 | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 53,373,000  
Fair Value as a Percentage of Net Assets [1] 0.80%  
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Equity | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1]   $ 123,060,000
Fair Value as a Percentage of Net Assets [1]   3.20%
Investment, Identifier [Axis]: Energy | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 176,710,000 $ 197,485,000 [3],[6]
Fair Value as a Percentage of Net Assets 2.60% 5.20% [3],[6]
Investment, Identifier [Axis]: Energy | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 7,713,000 $ 4,283,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.10% 0.10% [3]
Investment, Identifier [Axis]: Eucalyptus I HoldCo (CYM) L.P. | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 62,206,000 $ 34,762,000
Fair Value as a Percentage of Net Assets 0.90% 0.90%
Investment, Identifier [Axis]: Healthcare | Other Investment(s) in Debt 1 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 41,308,000 $ 33,875,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.60% 0.90% [3]
Investment, Identifier [Axis]: Healthcare | Other Investment(s) in Debt 2 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3],[4]   $ 4,156,000
Fair Value as a Percentage of Net Assets [3],[4]   0.10%
Investment, Identifier [Axis]: Industrials | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 11,673,000 $ 2,549,000 [3]
Fair Value as a Percentage of Net Assets 0.20% 0.10% [3]
Investment, Identifier [Axis]: Industrials | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [4] $ 34,994,000 $ 35,592,000 [3]
Fair Value as a Percentage of Net Assets [4] 0.50% 0.90% [3]
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt 1 | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 119,588,000  
Fair Value as a Percentage of Net Assets 1.80%  
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt 1 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3],[4] $ 124,416,000 $ 123,976,000
Fair Value as a Percentage of Net Assets [3],[4] 1.80% 3.20%
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt 2 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3],[4] $ 7,078,000 $ 5,149,000
Fair Value as a Percentage of Net Assets [3],[4] 0.10% 0.10%
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt 3 | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 2,504,000  
Fair Value as a Percentage of Net Assets 0.00%  
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt 3 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3],[4] $ 4,097,000 $ 2,136,000
Fair Value as a Percentage of Net Assets [3],[4] 0.10% 0.10%
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 112,436,000
Fair Value as a Percentage of Net Assets [3]   2.90%
Investment, Identifier [Axis]: Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [7] $ 6,421,142,000 $ 3,555,635,000
Fair Value as a Percentage of Net Assets [7] 101.60% 102.00%
Investment, Identifier [Axis]: Mercury Co-Invest L.P. | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 111,146,000 $ 88,966,000
Fair Value as a Percentage of Net Assets 1.60% 2.30%
Investment, Identifier [Axis]: Money Market Fund | Dreyfus Government Cash Management | Cash and Cash Equivalents | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Money Market Fund, Fair Value   $ 8,745,000
Money Market Fund, Fair Value as a Percentage of Net Assets   0.20%
Investment, Identifier [Axis]: Money Market Fund | Fidelity Investments Money Market Treasury | Cash and Cash Equivalents | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Money Market Fund, Fair Value $ 15,223,000 $ 4,737,000
Money Market Fund, Fair Value as a Percentage of Net Assets 0.20% 0.10%
Investment, Identifier [Axis]: Odyssey Holdco L.L.C. | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 406,463,000 $ 217,233,000
Fair Value as a Percentage of Net Assets 6.00% 5.70%
Investment, Identifier [Axis]: Poseidon Holdco I L.P. | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 52,448,000 $ 37,079,000
Fair Value as a Percentage of Net Assets 0.80% 1.00%
Investment, Identifier [Axis]: Real Estate | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 211,992,000  
Fair Value as a Percentage of Net Assets 3.10%  
Investment, Identifier [Axis]: Real Estate | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 8,076,000 $ 6,147,000 [4]
Fair Value as a Percentage of Net Assets [3] 0.10% 0.20% [4]
Investment, Identifier [Axis]: Technology, Media & Entertainment | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 9,929,000  
Fair Value as a Percentage of Net Assets 0.10%  
Investment, Identifier [Axis]: Technology, Media & Entertainment | Other Investment(s) in Equity | Various| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 23,088,000  
Fair Value as a Percentage of Net Assets [1] 0.30%  
Investment, Identifier [Axis]: Technology, Media and Entertainment | Other Investment(s) in Debt 1 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 52,978,000 $ 91,082,000 [4]
Fair Value as a Percentage of Net Assets [3] 0.80% 2.40% [4]
Investment, Identifier [Axis]: Technology, Media and Entertainment | Other Investment(s) in Debt 2 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 4,003,000 $ 3,015,000 [4]
Fair Value as a Percentage of Net Assets [3] 0.10% 0.10% [4]
Investment, Identifier [Axis]: Technology, Media and Entertainment | Other Investment(s) in Debt 3 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 3,649,000 $ 2,010,000 [4]
Fair Value as a Percentage of Net Assets [3] 0.10% 0.10% [4]
Investment, Identifier [Axis]: Technology, Media and Entertainment | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3]   $ 20,012,000
Fair Value as a Percentage of Net Assets [3]   0.50%
Investment, Identifier [Axis]: Transportation Infrastructure | Hieroglyphs L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1]   $ 222,041,000
Fair Value as a Percentage of Net Assets [1]   5.80%
Investment, Identifier [Axis]: Transportation Infrastructure | Mercury Co-Invest L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 578,533,000  
Fair Value as a Percentage of Net Assets [1] 8.60%  
Investment, Identifier [Axis]: Transportation Infrastructure | Mercury Co-Invest L.P. | Equity Investments| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1],[5]   $ 534,915,000
Fair Value as a Percentage of Net Assets [1],[5]   14.00%
Investment, Identifier [Axis]: Transportation Infrastructure | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 72,697,000 $ 65,836,000
Fair Value as a Percentage of Net Assets [3] 1.10% 1.70%
Investment, Identifier [Axis]: Transportation Infrastructure | Other Investment(s) in Equity | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 376,190,000 [6] $ 76,000
Fair Value as a Percentage of Net Assets [1] 5.60% [6] 0.00%
Investment, Identifier [Axis]: Transportation Infrastructure | Poseidon Holdco I L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 647,734,000  
Fair Value as a Percentage of Net Assets [1] 9.60%  
Investment, Identifier [Axis]: Transportation Infrastructure | Poseidon Holdco I L.P. | Equity Investments| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1],[5]   $ 580,177,000
Fair Value as a Percentage of Net Assets [1],[5]   15.20%
Investment, Identifier [Axis]: Transportation Infrastructure | Poseidon Seller 3 L.L.C. | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 75,345,000 $ 72,049,000
Fair Value as a Percentage of Net Assets [3] 1.10% 1.90%
Investment, Identifier [Axis]: Transportation | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [3] $ 17,094,000 $ 11,134,000 [4]
Fair Value as a Percentage of Net Assets [3] 0.30% 0.30% [4]
Investment, Identifier [Axis]: Various | Infrastructure Investments L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1],[2] $ 1,222,169,000 $ 790,228,000
Fair Value as a Percentage of Net Assets [1],[2] 18.10% 20.70%
Investment, Identifier [Axis]: Various | Other Investment(s) in Affiliated Investee Funds | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1],[2] $ 331,439,000 $ 130,251,000
Fair Value as a Percentage of Net Assets [1],[2] 4.90% 3.40%
Investment, Identifier [Axis]: Various | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value $ 12,034,000  
Fair Value as a Percentage of Net Assets 0.20%  
Investment, Identifier [Axis]: Various | SP Ibex Acquisitions L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1],[2] $ 523,777,000  
Fair Value as a Percentage of Net Assets [1],[2] 7.70%  
Investment, Identifier [Axis]: Water & Waste Infrastructure Infrastructure | Other Investment(s) in Equity | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Summary of Investment Holdings [Line Items]    
Fair Value [1] $ 204,516,000  
Fair Value as a Percentage of Net Assets [1] 3.00%  
[1] Equity Investments are generally considered equity interests, which include different forms of interests and rights and obligations that represent ownership in an entity or the right to acquire or dispose of ownership in an entity, including but not limited to (i) common equity, (ii) preferred equity, (iii) limited partner interest (iv) warrants and (v) other equity-linked securities.
[2] Fund investments are diversified and are not categorized to one industry.
[3] Includes different forms of interests that represent a creditor relationship with an investee, including but not limited to (1) bank loans, (2) interests in collateralized loan obligations and (3) direct lending debt investments.
[4] Investments that are generally liquid in nature are intended to be held for short durations and may be used to generate income, facilitate capital deployment or provide a potential source of liquidity. Industries may be diversified outside of infrastructure industries.
[5] BXINFRA holds additional interests in this investment through its investment in Infrastructure Investments L.P. BXINFRA’s proportional fair value and shares in the investee are provided in Note 3. “Investments and Fair Value Measurement.”
[6] There were no single investments included in this category that exceeded 5% of net assets of the Aggregator, BXINFRA U.S., the Feeder or a Parallel Fund (each as defined in Note 1. “Organization”).
[7] Refer to Note 3. “Investment in the Aggregator” for details on BXINFRA U.S.’s proportional share of investments through investees.