Securities - Gross Unrealized Losses and Fair Value of Company's Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	$ 2,440,094	$ 1,500,687
Unrealized losses less than 12 months	(229,538)	(21,993)
Fair value more than 12 months	178,921	35,281
Unrealized losses more than 12 months	(27,352)	(1,012)
Total fair value	2,619,015	1,535,968
Total unrealized losses	(256,890)	(23,005)
U.S. Treasury and federal agencies
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	517,187	268,732
Unrealized losses less than 12 months	(28,883)	(2,483)
Fair value more than 12 months	30,776	15,820
Unrealized losses more than 12 months	(2,473)	(430)
Total fair value	547,963	284,552
Total unrealized losses	(31,356)	(2,913)
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	1,057,290	539,882
Unrealized losses less than 12 months	(132,257)	(9,389)
Fair value more than 12 months	143,433	19,461
Unrealized losses more than 12 months	(24,518)	(582)
Total fair value	1,200,723	559,343
Total unrealized losses	(156,775)	(9,971)
Federal agency collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	94,156	56,027
Unrealized losses less than 12 months	(4,865)	(1,032)
Fair value more than 12 months	0	0
Unrealized losses more than 12 months	0	0
Total fair value	94,156	56,027
Total unrealized losses	(4,865)	(1,032)
Federal agency mortgage-backed pools
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	460,260	333,489
Unrealized losses less than 12 months	(37,110)	(3,644)
Fair value more than 12 months	4,712	0
Unrealized losses more than 12 months	(361)	0
Total fair value	464,972	333,489
Total unrealized losses	(37,471)	(3,644)
Private labeled mortgage-backed pools
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	117,409	113,057
Unrealized losses less than 12 months	(9,649)	(2,216)
Fair value more than 12 months	0	0
Unrealized losses more than 12 months	0	0
Total fair value	117,409	113,057
Total unrealized losses	(9,649)	(2,216)
Corporate notes
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	193,792	189,500
Unrealized losses less than 12 months	(16,774)	(3,229)
Fair value more than 12 months	0	0
Unrealized losses more than 12 months	0	0
Total fair value	193,792	189,500
Total unrealized losses	$ (16,774)	$ (3,229)