Securities - Debt Securities, Available-for-sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 8,456,620	$ 8,587,179
Unrealized Gains	3,056	36,492
Unrealized Losses	(542,371)	(112,447)
Allowance for Credit Losses	0
Fair Value	7,917,305	8,511,224
Government-sponsored residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,329,748	5,577,292
Unrealized Gains	264	17,918
Unrealized Losses	(360,666)	(70,502)
Allowance for Credit Losses	0
Fair Value	4,969,346	5,524,708
Government-sponsored commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,707,131	1,420,748
Unrealized Gains	0	760
Unrealized Losses	(91,204)	(12,640)
Allowance for Credit Losses	0
Fair Value	1,615,927	1,408,868
U.S. Agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,099,916	1,202,377
Unrealized Gains	0	1,067
Unrealized Losses	(86,017)	(28,430)
Allowance for Credit Losses	0
Fair Value	1,013,899	1,175,014
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	59,458	89,434
Unrealized Gains	0	5
Unrealized Losses	(3,223)	(834)
Allowance for Credit Losses	0
Fair Value	56,235	88,605
State and municipal bonds and obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	258,769	263,910
Unrealized Gains	2,792	16,460
Unrealized Losses	(1,245)	(41)
Allowance for Credit Losses	0
Fair Value	260,316	280,329
Small Business Administration pooled securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		31,821
Unrealized Gains		282
Unrealized Losses		0
Fair Value		32,103
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,598	1,597
Unrealized Gains	0	0
Unrealized Losses	(16)	0
Allowance for Credit Losses	0
Fair Value	$ 1,582	$ 1,597