Securities (Debt securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, [Line Items]
Debt securities available-for-sale, amortized cost	$ 5,853,160	$ 5,898,041
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	11,678	70,839
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(337,467)	(57,881)
Debt securities available for sale at fair value	5,527,371	5,910,999
Debt Securities, Held-to-Maturity, Amortized Cost	2,202,437	2,148,327
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	50
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	164,400	25,771
Debt Securities, Held-to-maturity, Fair Value	2,038,037	2,122,606
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Debt Securities, [Line Items]
Debt securities available-for-sale, amortized cost	3,604,576	3,738,616
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	8,315	45,077
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(205,237)	(38,092)
Debt securities available for sale at fair value	3,407,654	3,745,601
Debt Securities, Held-to-Maturity, Amortized Cost	2,202,437	2,148,327
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	50
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	164,400	25,771
Debt Securities, Held-to-maturity, Fair Value	2,038,037	2,122,606
Asset-backed Securities [Member]
Debt Securities, [Line Items]
Debt securities available-for-sale, amortized cost	433,879	469,052
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	377	3,802
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(26,209)	(9,791)
Debt securities available for sale at fair value	408,047	463,063
State and Municipal Securities [Member]
Debt Securities, [Line Items]
Debt securities available-for-sale, amortized cost	1,002,490	983,704
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,275	18,525
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(65,800)	(4,938)
Debt securities available for sale at fair value	938,965	997,291
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Debt Securities, [Line Items]
Debt securities available-for-sale, amortized cost	247,727	252,755
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	711	3,095
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(9,164)	(3,274)
Debt securities available for sale at fair value	239,274	252,576
US Treasury Securities [Member]
Debt Securities, [Line Items]
Debt securities available-for-sale, amortized cost	182,500	158,367
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(9,158)	(831)
Debt securities available for sale at fair value	173,342	157,536
Non-agency collateralized mortgage obligations [Member]
Debt Securities, [Line Items]
Debt securities available-for-sale, amortized cost	381,988	295,547
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	340
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(21,899)	(955)
Debt securities available for sale at fair value	$ 360,089	$ 294,932

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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Amount, before tax, of unrealized loss 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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