Securities - Schedule of Debt Securities Components (Details) - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020
Available-for-sale [Abstract]
Amortized Cost		$ 2,634,074	$ 2,437,513
Gross unrealized gains		134,220	150,074
Gross unrealized losses		2,259	282
Securities available for sale, at estimated fair value		2,766,035	2,587,305
HELD TO MATURITY
Amortized cost		94,850	108,998
Gross unrealized gains		6,518	9,200
Gross unrealized losses		0	0
Estimated Fair Value		101,368	118,198
US Treasury Securities
Available-for-sale [Abstract]
Amortized Cost		42,753
Gross unrealized gains		983
Gross unrealized losses		0
Securities available for sale, at estimated fair value		43,736
State and political subdivisions
Available-for-sale [Abstract]
Amortized Cost		1,765,231	1,475,030
Gross unrealized gains		101,074	105,601
Gross unrealized losses		1,426	37
Securities available for sale, at estimated fair value		1,864,879	1,580,594
HELD TO MATURITY
Amortized cost		908	907
Gross unrealized gains		5	13
Gross unrealized losses		0	0
Estimated Fair Value		913	920
Corporate bonds and other
Available-for-sale [Abstract]
Amortized Cost		112,387	77,224
Gross unrealized gains		2,191	1,053
Gross unrealized losses		331	22
Securities available for sale, at estimated fair value		114,247	78,255
Residential
Available-for-sale [Abstract]
Amortized Cost	[1]	606,765	771,409
Gross unrealized gains	[1]	26,387	38,674
Gross unrealized losses	[1]	252	73
Securities available for sale, at estimated fair value	[1]	632,900	810,010
HELD TO MATURITY
Amortized cost	[1]	42,171	47,948
Gross unrealized gains	[1]	3,002	4,187
Gross unrealized losses	[1]	0	0
Estimated Fair Value	[1]	45,173	52,135
Commercial
Available-for-sale [Abstract]
Amortized Cost	[1]	106,938	113,850
Gross unrealized gains	[1]	3,585	4,746
Gross unrealized losses	[1]	250	150
Securities available for sale, at estimated fair value	[1]	110,273	118,446
HELD TO MATURITY
Amortized cost	[1]	51,771	60,143
Gross unrealized gains	[1]	3,511	5,000
Gross unrealized losses	[1]	0	0
Estimated Fair Value	[1]	$ 55,282	$ 65,143

[1] All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs.