Securities - Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Available for sale
Amortized Cost	$ 1,186,135	$ 1,153,611
Gross Unrealized Gains	2,373	16,800
Gross Unrealized Losses	(75,996)	(9,599)
Fair Value	1,112,512	1,160,812
Held to maturity
Amortized Cost	2,006,129	1,552,443
Gross Unrealized Gains	2,610	20,954
Gross Unrealized Losses	(180,894)	(13,406)
Fair Value	1,827,845	1,559,991
U.S. Treasury and federal agencies
Available for sale
Amortized Cost	293,914	118,595
Gross Unrealized Gains	0	82
Gross Unrealized Losses	(11,394)	(1,698)
Fair Value	282,520	116,979
Held to maturity
Amortized Cost	292,459	195,429
Gross Unrealized Gains	0	12
Gross Unrealized Losses	(19,962)	(1,215)
Fair Value	272,497	194,226
State and municipal
Available for sale
Amortized Cost	510,936	632,652
Gross Unrealized Gains	1,687	12,802
Gross Unrealized Losses	(43,571)	(5,708)
Fair Value	469,052	639,746
Held to maturity
Amortized Cost	1,091,037	862,461
Gross Unrealized Gains	2,610	20,719
Gross Unrealized Losses	(113,204)	(4,263)
Fair Value	980,443	878,917
Federal agency collateralized mortgage obligations
Available for sale
Amortized Cost	50,201	60,600
Gross Unrealized Gains	20	989
Gross Unrealized Losses	(629)	(12)
Fair Value	49,592	61,577
Held to maturity
Amortized Cost	56,841	48,482
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(4,236)	(1,020)
Fair Value	52,605	47,465
Federal agency mortgage-backed pools
Available for sale
Amortized Cost	216,411	225,329
Gross Unrealized Gains	138	1,777
Gross Unrealized Losses	(14,114)	(1,032)
Fair Value	202,435	226,074
Held to maturity
Amortized Cost	302,407	188,426
Gross Unrealized Gains	0	151
Gross Unrealized Losses	(23,357)	(2,612)
Fair Value	279,050	185,965
Private labeled mortgage-backed pools
Available for sale
Amortized Cost	30,239	31,856
Gross Unrealized Gains	84	137
Gross Unrealized Losses	(1,690)	(376)
Fair Value	28,633	31,617
Held to maturity
Amortized Cost	98,719	99,958
Gross Unrealized Gains	0	58
Gross Unrealized Losses	(7,959)	(1,840)
Fair Value	90,760	98,176
Corporate notes
Available for sale
Amortized Cost	84,434	84,579
Gross Unrealized Gains	444	1,013
Gross Unrealized Losses	(4,598)	(773)
Fair Value	80,280	84,819
Held to maturity
Amortized Cost	164,666	157,687
Gross Unrealized Gains	0	11
Gross Unrealized Losses	(12,176)	(2,456)
Fair Value	$ 152,490	$ 155,242

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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