Securities - Summary of Book Values and Fair Values of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value
Amortized Cost	$ 2,662,481	$ 1,432,684
Fair Value	2,630,414	1,453,132
Unrealized Gains	10,595	22,963
Unrealized (Losses)	(42,662)	(2,515)
Securities held to maturity:
Amortized Cost	513,825	167,551
Fair Value	511,699	170,734
Unrealized Gains	3,540	3,348
Unrealized (Losses)	(5,666)	(165)
Government-sponsored enterprise securities
Fair Value
Amortized Cost	71,951	70,016
Fair Value	69,179	70,206
Unrealized Gains	0	371
Unrealized (Losses)	(2,772)	(181)
Mortgage-backed securities
Fair Value
Amortized Cost	2,545,150	1,318,998
Fair Value	2,514,805	1,337,706
Unrealized Gains	9,489	20,832
Unrealized (Losses)	(39,834)	(2,124)
Securities held to maturity:
Amortized Cost	20,260	29,959
Fair Value	20,845	30,900
Unrealized Gains	585	941
Unrealized (Losses)	0	0
Corporate bonds
Fair Value
Amortized Cost	45,380	43,670
Fair Value	46,430	45,220
Unrealized Gains	1,106	1,760
Unrealized (Losses)	(56)	(210)
State and local governments
Securities held to maturity:
Amortized Cost	493,565	137,592
Fair Value	490,854	139,834
Unrealized Gains	2,955	2,407
Unrealized (Losses)	$ (5,666)	$ (165)

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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