Securities - Summary Of Debt Securities (Detail) - USD ($)	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 5,358,289,000	$ 7,825,435,000
Unrealized Gains	15,000	9,000
Unrealized Losses	(838,011,000)	(1,134,666,000)
Allowance for Credit Losses	0	0	$ 0
Fair Value	4,520,293,000	6,690,778,000
Government-sponsored residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,470,727,000	4,855,763,000
Unrealized Gains	0	0
Unrealized Losses	(579,663,000)	(743,855,000)
Allowance for Credit Losses	0	0
Fair Value	2,891,064,000	4,111,908,000
Government-sponsored commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,354,187,000	1,570,119,000
Unrealized Gains	0	0
Unrealized Losses	(214,027,000)	(221,165,000)
Allowance for Credit Losses	0	0
Fair Value	1,140,160,000	1,348,954,000
U.S. Agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	235,844,000	1,100,891,000
Unrealized Gains	0	0
Unrealized Losses	(25,774,000)	(148,409,000)
Allowance for Credit Losses	0	0
Fair Value	210,070,000	952,482,000
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	99,437,000	99,324,000
Unrealized Gains	0	0
Unrealized Losses	(6,355,000)	(6,267,000)
Allowance for Credit Losses	0	0
Fair Value	93,082,000	93,057,000
State and municipal bonds and obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	197,994,000	198,039,000
Unrealized Gains	15,000	9,000
Unrealized Losses	(12,192,000)	(14,956,000)
Allowance for Credit Losses	0	0
Fair Value	185,817,000	183,092,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	100,000	1,299,000
Unrealized Gains	0	0
Unrealized Losses	0	(14,000)
Allowance for Credit Losses	0	0
Fair Value	$ 100,000	$ 1,285,000