Investment Securities - Amortized Cost and Fair Value, by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Amortized Cost
Due in one year or less	$ 30,106
Due after one year through five years	79,915
Due after five years through ten years	177,556
Due after ten years	172,414
Total contractual maturities	459,991
Available-for-sale investment securities, amortized cost	4,267,809	$ 8,560,733
Fair Value
Due in one year or less	29,762
Due after one year through five years	77,983
Due after five years through ten years	170,656
Due after ten years	168,980
Total contractual maturities	447,381
Total available-for-sale securities, Fair value,	3,967,746	8,428,032
Amortized Cost
Due after ten years	108,788
Total contractual maturities	108,788
Amortized cost	4,093,215
Fair Value
Due after ten years	102,539
Total contractual maturities	102,539
Total held to maturity, Fair value,	3,910,780	0
Mortgage-backed securities:
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,960,919
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,810,466
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,344,662
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,269,202
Residential - Government agency
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	72,027
Available-for-sale investment securities, amortized cost	72,027	135,764
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	67,958
Total available-for-sale securities, Fair value,	67,958	137,264
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	47,309
Amortized cost	47,309
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	44,278
Total held to maturity, Fair value,	44,278
Residential - Government-sponsored enterprises
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,444,461
Available-for-sale investment securities, amortized cost	1,444,461	1,496,605
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,333,015
Total available-for-sale securities, Fair value,	1,333,015	1,491,100
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	93,458
Amortized cost	93,458
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	87,341
Total held to maturity, Fair value,	87,341
Commercial - Government agency
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	297,271
Available-for-sale investment securities, amortized cost	297,271	392,443
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	267,657
Total available-for-sale securities, Fair value,	267,657	387,663
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	30,497
Amortized cost	30,497
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	27,812
Total held to maturity, Fair value,	27,812
Commercial - Government-sponsored enterprises
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	147,160
Available-for-sale investment securities, amortized cost	147,160	1,415,511
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	141,836
Total available-for-sale securities, Fair value,	141,836	1,369,443
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,173,398
Amortized cost	1,173,398
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,109,771
Total held to maturity, Fair value,	1,109,771
Collateralized mortgage obligations
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,846,899
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,709,899
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	2,639,765
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	2,539,039
Government agency
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,102,277
Available-for-sale investment securities, amortized cost	1,102,277	2,103,187
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,025,339
Total available-for-sale securities, Fair value,	1,025,339	2,079,523
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	879,010
Amortized cost	879,010
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	847,767
Total held to maturity, Fair value,	847,767
Government-sponsored enterprises
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	744,622
Available-for-sale investment securities, amortized cost	744,622	2,671,131
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	684,560
Total available-for-sale securities, Fair value,	684,560	$ 2,621,044
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,760,755
Amortized cost	1,760,755
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,691,272
Total held to maturity, Fair value,	$ 1,691,272