Investment Securities - Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Debt Securities Held to Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 3,073,205	$ 2,668,697
Gross Unrealized Gains	5,228	25,980
Gross Unrealized Losses	(164,582)	(34,072)
Fair Value	2,913,851	2,660,605
U.S. Treasury securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	67,401	67,558
Gross Unrealized Gains	1,531	4,103
Gross Unrealized Losses	0	0
Fair Value	68,932	71,661
U.S. government agency securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,572	6,265
Gross Unrealized Gains	0	113
Gross Unrealized Losses	(119)	0
Fair Value	5,453	6,378
Obligations of states and state agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	132,017	141,015
Gross Unrealized Gains	648	3,065
Gross Unrealized Losses	(1,054)	(312)
Fair Value	131,611	143,768
Municipal bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	187,143	196,947
Gross Unrealized Gains	871	3,536
Gross Unrealized Losses	(1,604)	(87)
Fair Value	186,410	200,396
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	319,160	337,962
Gross Unrealized Gains	1,519	6,601
Gross Unrealized Losses	(2,658)	(399)
Fair Value	318,021	344,164
Residential mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,594,295	2,166,142
Gross Unrealized Gains	1,993	14,599
Gross Unrealized Losses	(155,790)	(28,440)
Fair Value	2,440,498	2,152,301
Trust preferred securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	37,027	37,020
Gross Unrealized Gains	4	5
Gross Unrealized Losses	(5,298)	(5,109)
Fair Value	31,733	31,916
Corporate and other debt securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	49,750	53,750
Gross Unrealized Gains	181	559
Gross Unrealized Losses	(717)	(124)
Fair Value	$ 49,214	$ 54,185

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

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