v3.26.3
Investments and Fair Value Measurement - Schedule of Investments (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Schedule of Investments [Line Items]    
Fair Value $ 6,421,142 $ 3,555,635
Fair Value as a Percentage of Net Assets 101.60% 102.00%
Investment, Identifier [Axis]: Consumer and Services | Other Investment(s) in Debt 1 | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 41,030 $ 29,670
Fair Value as a Percentage of Net Assets [1] 0.60% 0.80%
Investment, Identifier [Axis]: Consumer and Services | Other Investment(s) in Debt 1 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [2] $ 143,861 $ 128,251 [1]
Fair Value as a Percentage of Net Assets [2] 2.10% 3.40% [1]
Investment, Identifier [Axis]: Consumer and Services | Other Investment(s) in Debt 2 | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 13,794 $ 9,738
Fair Value as a Percentage of Net Assets [1] 0.20% 0.30%
Investment, Identifier [Axis]: Consumer and Services | Other Investment(s) in Debt 2 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [2] $ 9,740 $ 9,014 [1]
Fair Value as a Percentage of Net Assets [2] 0.10% 0.20% [1]
Investment, Identifier [Axis]: Digital Infrastructure | Aspen Holdco III L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 342,128  
Investment owned, balance, shares (in shares) 338,731  
Fair Value as a Percentage of Net Assets [3] 5.10%  
Investment, Identifier [Axis]: Digital Infrastructure | Eucalyptus I HoldCo (CYM) L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3],[4] $ 489,514  
Investment owned, balance, shares (in shares) 1,637,829,061,453  
Fair Value as a Percentage of Net Assets [3],[4] 7.20%  
Investment, Identifier [Axis]: Digital Infrastructure | Eucalyptus I HoldCo (CYM) L.P. | Equity Investments| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3]   $ 346,583
Investment owned, balance, shares (in shares) [3]   1,637,829,051,635
Fair Value as a Percentage of Net Assets [3]   9.10%
Investment, Identifier [Axis]: Digital Infrastructure | Odyssey Holdco L.L.C. | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 12,207 $ 25,001 [1]
Fair Value as a Percentage of Net Assets 0.20% 0.70% [1]
Investment, Identifier [Axis]: Digital Infrastructure | Odyssey Holdco L.L.C. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 415,605  
Investment owned, balance, shares (in shares) 1,077,009  
Fair Value as a Percentage of Net Assets [3] 6.10%  
Investment, Identifier [Axis]: Digital Infrastructure | Odyssey Holdco L.L.C. | Equity Investments| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3],[4]   $ 244,587
Investment owned, balance, shares (in shares) [3],[4]   811,288
Fair Value as a Percentage of Net Assets [3],[4]   6.40%
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 90,542 $ 101,724 [1]
Fair Value as a Percentage of Net Assets 1.30% 2.70% [1]
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [2] $ 3,975 $ 2,135 [1]
Fair Value as a Percentage of Net Assets [2] 0.10% 0.10% [1]
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Equity 1 | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 291,560  
Fair Value as a Percentage of Net Assets [3] 4.30%  
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Equity 2 | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 759  
Fair Value as a Percentage of Net Assets [3] 0.00%  
Investment, Identifier [Axis]: Digital Infrastructure | Other Investment(s) in Equity | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3]   $ 21,259
Fair Value as a Percentage of Net Assets [3]   0.60%
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 101,622 $ 62,031 [1]
Fair Value as a Percentage of Net Assets 1.50% 1.60% [1]
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [2] $ 6,086 $ 6,408 [1]
Fair Value as a Percentage of Net Assets [2] 0.10% 0.20% [1]
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Equity 1 | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 148,431  
Fair Value as a Percentage of Net Assets [3] 2.20%  
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Equity 2 | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 53,373  
Fair Value as a Percentage of Net Assets [3] 0.80%  
Investment, Identifier [Axis]: Energy Infrastructure | Other Investment(s) in Equity | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3]   $ 123,060
Fair Value as a Percentage of Net Assets [3]   3.20%
Investment, Identifier [Axis]: Energy | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 176,710 $ 197,485 [1],[5]
Fair Value as a Percentage of Net Assets 2.60% 5.20% [1],[5]
Investment, Identifier [Axis]: Energy | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [2] $ 7,713 $ 4,283 [1]
Fair Value as a Percentage of Net Assets [2] 0.10% 0.10% [1]
Investment, Identifier [Axis]: Eucalyptus I HoldCo (CYM) L.P. | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 62,206 $ 34,762
Investment owned, balance, shares (in shares) 186,696,522,949 165,605,569,717
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.    
Schedule of Investments [Line Items]    
Fair Value [2] $ 41,308 $ 33,875 [1]
Fair Value as a Percentage of Net Assets [2] 0.60% 0.90% [1]
Investment, Identifier [Axis]: Healthcare | Other Investment(s) in Debt 2 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1],[2]   $ 4,156
Fair Value as a Percentage of Net Assets [1],[2]   0.10%
Investment, Identifier [Axis]: Industrials | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 11,673 $ 2,549 [1]
Fair Value as a Percentage of Net Assets 0.20% 0.10% [1]
Investment, Identifier [Axis]: Industrials | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [2] $ 34,994 $ 35,592 [1]
Fair Value as a Percentage of Net Assets [2] 0.50% 0.90% [1]
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt 1 | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 119,588  
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.    
Schedule of Investments [Line Items]    
Fair Value [1],[2] $ 124,416 $ 123,976
Fair Value as a Percentage of Net Assets [1],[2] 1.80% 3.20%
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt 2 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1],[2] $ 7,078 $ 5,149
Fair Value as a Percentage of Net Assets [1],[2] 0.10% 0.10%
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt 3 | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 2,504  
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.    
Schedule of Investments [Line Items]    
Fair Value [1],[2] $ 4,097 $ 2,136
Fair Value as a Percentage of Net Assets [1],[2] 0.10% 0.10%
Investment, Identifier [Axis]: Infrastructure Services | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1]   $ 112,436
Fair Value as a Percentage of Net Assets [1]   2.90%
Investment, Identifier [Axis]: Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [6] $ 6,421,142 $ 3,555,635
Investment owned, balance, shares (in shares) [6] 204,506,119 129,060,376
Fair Value as a Percentage of Net Assets [6] 101.60% 102.00%
Investment, Identifier [Axis]: Mercury Co-Invest L.P. | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 111,146 $ 88,966
Investment owned, balance, shares (in shares) 148,048 131,326
Fair Value as a Percentage of Net Assets 1.60% 2.30%
Investment, Identifier [Axis]: Odyssey Holdco L.L.C. | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 406,463 $ 217,233
Investment owned, balance, shares (in shares) 832,860 719,237
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.    
Schedule of Investments [Line Items]    
Fair Value $ 52,448 $ 37,079
Investment owned, balance, shares (in shares) 39,362 32,214
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.    
Schedule of Investments [Line Items]    
Fair Value $ 211,992  
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.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 8,076 $ 6,147 [2]
Fair Value as a Percentage of Net Assets [1] 0.10% 0.20% [2]
Investment, Identifier [Axis]: Technology, Media & Entertainment | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 9,929  
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.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 23,088  
Fair Value as a Percentage of Net Assets [3] 0.30%  
Investment, Identifier [Axis]: Technology, Media and Entertainment | Other Investment(s) in Debt 1 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 52,978 $ 91,082 [2]
Fair Value as a Percentage of Net Assets [1] 0.80% 2.40% [2]
Investment, Identifier [Axis]: Technology, Media and Entertainment | Other Investment(s) in Debt 2 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 4,003 $ 3,015 [2]
Fair Value as a Percentage of Net Assets [1] 0.10% 0.10% [2]
Investment, Identifier [Axis]: Technology, Media and Entertainment | Other Investment(s) in Debt 3 | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 3,649 $ 2,010 [2]
Fair Value as a Percentage of Net Assets [1] 0.10% 0.10% [2]
Investment, Identifier [Axis]: Technology, Media and Entertainment | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1]   $ 20,012
Fair Value as a Percentage of Net Assets [1]   0.50%
Investment, Identifier [Axis]: Transportation Infrastructure | Hieroglyphs L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3]   $ 222,041
Investment owned, balance, shares (in shares) [3]   220
Fair Value as a Percentage of Net Assets [3]   5.80%
Investment, Identifier [Axis]: Transportation Infrastructure | Mercury Co-Invest L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 578,533  
Investment owned, balance, shares (in shares) 859,082  
Fair Value as a Percentage of Net Assets [3] 8.60%  
Investment, Identifier [Axis]: Transportation Infrastructure | Mercury Co-Invest L.P. | Equity Investments| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3],[4]   $ 534,915
Investment owned, balance, shares (in shares) [3],[4]   783,265
Fair Value as a Percentage of Net Assets [3],[4]   14.00%
Investment, Identifier [Axis]: Transportation Infrastructure | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 72,697 $ 65,836
Fair Value as a Percentage of Net Assets [1] 1.10% 1.70%
Investment, Identifier [Axis]: Transportation Infrastructure | Other Investment(s) in Equity | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 376,190 [5] $ 76
Fair Value as a Percentage of Net Assets [3] 5.60% [5] 0.00%
Investment, Identifier [Axis]: Transportation Infrastructure | Poseidon Holdco I L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 647,734  
Investment owned, balance, shares (in shares) 541,921  
Fair Value as a Percentage of Net Assets [3] 9.60%  
Investment, Identifier [Axis]: Transportation Infrastructure | Poseidon Holdco I L.P. | Equity Investments| Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3],[4]   $ 580,177
Investment owned, balance, shares (in shares) [3],[4]   500,000
Fair Value as a Percentage of Net Assets [3],[4]   15.20%
Investment, Identifier [Axis]: Transportation Infrastructure | Poseidon Seller 3 L.L.C. | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 75,345 $ 72,049
Fair Value as a Percentage of Net Assets [1] 1.10% 1.90%
Investment, Identifier [Axis]: Transportation | Other Investment(s) in Debt | Debt Investments - Liquid | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [1] $ 17,094 $ 11,134 [2]
Fair Value as a Percentage of Net Assets [1] 0.30% 0.30% [2]
Investment, Identifier [Axis]: Various | Infrastructure Investments L.P. | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3],[7] $ 1,222,169 $ 790,228
Investment owned, balance, shares (in shares) [7] 794,892 640,423
Fair Value as a Percentage of Net Assets [3],[7] 18.10% 20.70%
Investment, Identifier [Axis]: Various | Other Investment(s) in Affiliated Investee Funds | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3],[7] $ 331,439 $ 130,251
Fair Value as a Percentage of Net Assets [3],[7] 4.90% 3.40%
Investment, Identifier [Axis]: Various | Other Investment(s) in Debt | Debt Investments - Infrastructure | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value $ 12,034  
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.    
Schedule of Investments [Line Items]    
Fair Value [3],[7] $ 523,777  
Investment owned, balance, shares (in shares) [7] 850,000,000  
Fair Value as a Percentage of Net Assets [3],[7] 7.70%  
Investment, Identifier [Axis]: Water & Waste Infrastructure Infrastructure | Other Investment(s) in Equity | Equity Investments | Affiliated Investments | BXINFRA Aggregator (CYM) L.P.    
Schedule of Investments [Line Items]    
Fair Value [3] $ 204,516  
Fair Value as a Percentage of Net Assets [3] 3.00%  
[1] 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.
[2] 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.
[3] 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.
[4] 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.”
[5] 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”).
[6] Refer to Note 3. “Investment in the Aggregator” for details on BXINFRA U.S.’s proportional share of investments through investees.
[7] Fund investments are diversified and are not categorized to one industry.