Investment Securities Available for Sale - Amortized Cost And Estimated Fair Value By Contractual Maturity Of Investment Securities Available For Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Amortized Cost
Amortized cost, within one year	$ 24,566
Amortized cost, 1 to 5 years	1,051,478
Amortized cost, 5 to 10 years	439,954
Amortized cost, more than 10 years	9,757,329
Amortized Cost	11,273,327	$ 10,991,506
Fair Value
Fair value, within one year	24,566
Fair value, 1 to 5 years	981,495
Fair value, 5 to 10 years	386,996
Fair value, more than 10 years	8,285,046
Total fair value	9,678,103	10,918,329
U.S. Treasury securities
Amortized Cost
Amortized cost, within one year	24,293
Amortized cost, 1 to 5 years	441,804
Amortized cost, 5 to 10 years	49,856
Amortized cost, more than 10 years	0
Amortized Cost	515,953	120,465
Fair Value
Fair value, within one year	24,293
Fair value, 1 to 5 years	407,430
Fair value, 5 to 10 years	40,090
Fair value, more than 10 years	0
Total fair value	471,813	117,838
U.S. Government agency securities
Amortized Cost
Amortized cost, within one year	273
Amortized cost, 1 to 5 years	22,148
Amortized cost, 5 to 10 years	29,990
Amortized cost, more than 10 years	0
Amortized Cost	52,411	53,214
Fair Value
Fair value, within one year	273
Fair value, 1 to 5 years	19,588
Fair value, 5 to 10 years	28,937
Fair value, more than 10 years	0
Total fair value	48,798	54,201
Mortgage-backed securities issued by U.S. Government agencies
Amortized Cost
Amortized cost, within one year	0
Amortized cost, 1 to 5 years	534
Amortized cost, 5 to 10 years	4
Amortized cost, more than 10 years	904,055
Amortized Cost	904,593	790,329
Fair Value
Fair value, within one year	0
Fair value, 1 to 5 years	517
Fair value, 5 to 10 years	4
Fair value, more than 10 years	792,228
Total fair value	792,749	779,633
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Amortized Cost
Amortized cost, within one year	0
Amortized cost, 1 to 5 years	4,659
Amortized cost, 5 to 10 years	109,583
Amortized cost, more than 10 years	8,030,132
Amortized Cost	8,144,374	8,063,890
Fair Value
Fair value, within one year	0
Fair value, 1 to 5 years	4,451
Fair value, 5 to 10 years	102,400
Fair value, more than 10 years	6,788,219
Total fair value	6,895,070	8,012,301
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Amortized Cost
Amortized cost, within one year	0
Amortized cost, 1 to 5 years	91
Amortized cost, 5 to 10 years	12,293
Amortized cost, more than 10 years	757,114
Amortized Cost	769,498	951,691
Fair Value
Fair value, within one year	0
Fair value, 1 to 5 years	88
Fair value, 5 to 10 years	11,808
Fair value, more than 10 years	643,231
Total fair value	655,127	939,623
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Amortized Cost
Amortized cost, within one year	0
Amortized cost, 1 to 5 years	573,334
Amortized cost, 5 to 10 years	238,228
Amortized cost, more than 10 years	66,028
Amortized Cost	877,590	479,420
Fair Value
Fair value, within one year	0
Fair value, 1 to 5 years	540,820
Fair value, 5 to 10 years	203,757
Fair value, more than 10 years	61,368
Total fair value	805,945	481,744
Corporate debt securities and other debt securities
Amortized Cost
Amortized cost, within one year	0
Amortized cost, 1 to 5 years	8,908
Amortized cost, 5 to 10 years	0
Amortized cost, more than 10 years	0
Amortized Cost	8,908	18,309
Fair Value
Fair value, within one year	0
Fair value, 1 to 5 years	8,601
Fair value, 5 to 10 years	0
Fair value, more than 10 years	0
Total fair value	$ 8,601	$ 18,801