Investment Securities - Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Debt Securities Held to Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	$ 2,668,697	$ 2,173,011
Gross Unrealized Gains	25,980	62,326
Gross Unrealized Losses	(34,072)	(7,725)
Fair Value	2,660,605	2,227,612
U.S. Treasury securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	67,558	68,126
Gross Unrealized Gains	4,103	7,358
Gross Unrealized Losses	0	0
Fair Value	71,661	75,484
U.S. government agency securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	6,265	6,222
Gross Unrealized Gains	113	291
Gross Unrealized Losses	0	0
Fair Value	6,378	6,513
Obligations of states and state agencies
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	141,015	262,762
Gross Unrealized Gains	3,065	8,060
Gross Unrealized Losses	(312)	(105)
Fair Value	143,768	270,717
Municipal bonds
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	196,947	207,497
Gross Unrealized Gains	3,536	6,292
Gross Unrealized Losses	(87)	0
Fair Value	200,396	213,789
Obligations of states and political subdivisions
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	337,962	470,259
Gross Unrealized Gains	6,601	14,352
Gross Unrealized Losses	(399)	(105)
Fair Value	344,164	484,506
Residential mortgage-backed securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	2,166,142	1,550,306
Gross Unrealized Gains	14,599	39,603
Gross Unrealized Losses	(28,440)	(254)
Fair Value	2,152,301	1,589,655
Trust preferred securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	37,020	37,348
Gross Unrealized Gains	5	50
Gross Unrealized Losses	(5,109)	(7,365)
Fair Value	31,916	30,033
Corporate and other debt securities
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	53,750	40,750
Gross Unrealized Gains	559	672
Gross Unrealized Losses	(124)	(1)
Fair Value	$ 54,185	$ 41,421

Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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