v3.26.3
Investments in Limited Partnerships - Additional Information (Detail)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
Partnership
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Schedule of Investments [Line Items]          
Unfunded equity commitments in other liabilities $ 24,382,935   $ 24,382,935   $ 23,664,420
Tax benefits including low-income housing and historic tax credits 23,710 $ 19,737 71,345 $ 32,623  
Partnerships losses and impairment $ 3,100 $ 3,000 $ 9,300 $ 7,900  
Number of limited partnerships held | Partnership     3    
Investment Program, Proportional Amortization Method, Applied, Amortization Expense, Statement of Cash Flows [Extensible Enumeration] Tax benefits including low-income housing and historic tax credits Tax benefits including low-income housing and historic tax credits Tax benefits including low-income housing and historic tax credits Tax benefits including low-income housing and historic tax credits  
Equity Method Investments [Member]          
Schedule of Investments [Line Items]          
Tax benefits including low-income housing and historic tax credits     $ 11,600 $ 9,900  
Limited Liability Company [Member]          
Schedule of Investments [Line Items]          
Amount invested in partnerships $ 4,200   4,200   4,000
Variable Interest Entity, Not Primary Beneficiary [Member]          
Schedule of Investments [Line Items]          
Unfunded equity commitments in other liabilities 34,700   34,700   37,500
Variable Interest Entity, Not Primary Beneficiary [Member] | Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherAssets          
Schedule of Investments [Line Items]          
Amount invested in partnerships $ 85,500   $ 85,500   $ 83,700