Investments in Limited Partnerships - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) Partnership	Jun. 30, 2024 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Schedule of Investments [Line Items]
Unfunded equity commitments in other liabilities	$ 23,752,356		$ 23,752,356			$ 15,894,017
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
Investment Program, Proportional Amortization Method, Applied, Amortization Expense, Statement of Income or Comprehensive Income [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
Partnerships losses and impairment	$ 3,000	$ 1,200	$ 4,900	$ 2,300
Number of limited partnerships held | Partnership			3
Equity Method Investments [Member]
Schedule of Investments [Line Items]
Income tax credits and adjustments						4,300
Equity Method Investments [Member] | Forecast [Member]
Schedule of Investments [Line Items]
Income tax credits and adjustments					$ 10,300
Limited Liability Company [Member]
Schedule of Investments [Line Items]
Amount invested in partnerships	3,700		$ 3,700			2,900
Limited Liability Company [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Investments [Line Items]
Partnership income (loss) under equity method	72	$ 12	77	$ (11)
Variable Interest Entity, Not Primary Beneficiary [Member]
Schedule of Investments [Line Items]
Unfunded equity commitments in other liabilities	33,200		33,200			19,000
Variable Interest Entity, Not Primary Beneficiary [Member] | Other Assets [Member]
Schedule of Investments [Line Items]
Amount invested in partnerships	$ 79,800		$ 79,800			$ 38,200