Securities - Amortized Cost and Fair Value of Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Amortized cost and fair value of securities available for sale
Amortized Cost	$ 2,554,976	$ 2,400,956
Gross Unrealized Gains	2,843	16,120
Gross Unrealized Losses	(152,503)	(31,024)
Fair Value	2,405,316	2,386,052
U.S. Treasury securities
Amortized cost and fair value of securities available for sale
Amortized Cost	2,000	3,007
Gross Unrealized Gains	0	3
Gross Unrealized Losses	0	0
Fair Value	2,000	3,010
Obligations of other U.S. Government agencies and corporations
Amortized cost and fair value of securities available for sale
Amortized Cost		153,847
Gross Unrealized Gains		5,532
Gross Unrealized Losses		(269)
Fair Value		159,110
Obligations of states and political subdivisions
Amortized cost and fair value of securities available for sale
Amortized Cost	161,565	0
Gross Unrealized Gains	1,117	0
Gross Unrealized Losses	(5,205)	0
Fair Value	157,477	0
Trust preferred securities
Amortized cost and fair value of securities available for sale
Amortized Cost		0
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		0
Other debt securities
Amortized cost and fair value of securities available for sale
Amortized Cost	94,996	36,515
Gross Unrealized Gains	385	1,097
Gross Unrealized Losses	(1,991)	(148)
Fair Value	93,390	37,464
Government agency mortgage backed securities \| Residential mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	969,140	967,497
Gross Unrealized Gains	1,249	7,854
Gross Unrealized Losses	(48,493)	(6,816)
Fair Value	921,896	968,535
Government agency mortgage backed securities \| Commercial mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	11,277	14,717
Gross Unrealized Gains	0	365
Gross Unrealized Losses	(371)	(1)
Fair Value	10,906	15,081
Government agency collateralized mortgage obligations \| Residential mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	1,094,043	1,008,514
Gross Unrealized Gains	5	457
Gross Unrealized Losses	(83,591)	(20,371)
Fair Value	1,010,457	988,600
Government agency collateralized mortgage obligations \| Commercial mortgage backed securities:
Amortized cost and fair value of securities available for sale
Amortized Cost	221,955	216,859
Gross Unrealized Gains	87	812
Gross Unrealized Losses	(12,852)	(3,419)
Fair Value	$ 209,190	$ 214,252

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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Amortized cost of 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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