Securities - Summary Of Debt Securities (Detail) - USD ($)	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 5,459,320,000	$ 7,825,435,000
Unrealized Gains	119,000	9,000
Unrealized Losses	(759,305,000)	(1,134,666,000)
Allowance for Credit Losses	0	0	$ 0
Fair Value	4,700,134,000	6,690,778,000
Government-sponsored residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,557,844,000	4,855,763,000
Unrealized Gains	0	0
Unrealized Losses	(533,284,000)	(743,855,000)
Allowance for Credit Losses	0	0
Fair Value	3,024,560,000	4,111,908,000
Government-sponsored commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,367,239,000	1,570,119,000
Unrealized Gains	0	0
Unrealized Losses	(187,199,000)	(221,165,000)
Allowance for Credit Losses	0	0
Fair Value	1,180,040,000	1,348,954,000
U.S. Agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	235,540,000	1,100,891,000
Unrealized Gains	0	0
Unrealized Losses	(23,733,000)	(148,409,000)
Allowance for Credit Losses	0	0
Fair Value	211,807,000	952,482,000
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	99,380,000	99,324,000
Unrealized Gains	1,000	0
Unrealized Losses	(5,098,000)	(6,267,000)
Allowance for Credit Losses	0	0
Fair Value	94,283,000	93,057,000
State and municipal bonds and obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	198,017,000	198,039,000
Unrealized Gains	118,000	9,000
Unrealized Losses	(9,986,000)	(14,956,000)
Allowance for Credit Losses	0	0
Fair Value	188,149,000	183,092,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,300,000	1,299,000
Unrealized Gains	0	0
Unrealized Losses	(5,000)	(14,000)
Allowance for Credit Losses	0	0
Fair Value	$ 1,295,000	$ 1,285,000