Securities Available for Sale and Held to Maturity - Contractual Maturities of Available for Sale and Held to Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Securities Available for Sale, Amortized Cost [Abstract]
Due in one year or less	$ 1,524
Due after one year through five years	243,531
Due after five years through ten years	113,074
Due after ten years	10,611
Total amortized cost, before mortgage-backed securities	368,740
Mortgage-backed securities	2,887,549
Securities Available for Sale, Amortized Cost	3,256,289	$ 1,959,773
Securities Available for Sale, Estimated Fair Value [Abstract]
Due in one year or less	1,534
Due after one year through five years	240,494
Due after five years through ten years	111,752
Due after ten years	10,301
Total fair value, before mortgage-backed securities	364,081
Mortgage-backed securities	2,874,796
Total	3,238,877	1,991,815
Securities Held to Maturity, Amortized Cost [Abstract]
Due in one year or less	2,809
Due after one year through five years	4,519
Total amortized cost, before mortgage-backed securities	7,328
Mortgage-backed securities	335,209
Securities Held to Maturity, Amortized Cost	342,537	538,072
Securities Held to Maturity, Estimated Fair Value [Abstract]
Due in one year or less	2,827
Due after one year through five years	4,562
Total fair value, before mortgage-backed securities	7,389
Mortgage-backed securities	346,122
Total	$ 353,511	$ 563,115