Income Taxes - Summary of Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal income tax at expected statutory rate	$ 111,314	$ 95,927	$ 69,235
State income tax expense, net of federal tax effect	36,744	32,581	23,851
Tax-exempt interest, net of interest incurred to carry tax-exempt securities	(2,786)	(3,118)	(3,974)
Bank owned life insurance	(2,026)	(1,637)	(1,734)
Tax credits from securities and other investments	(10,071)	(11,636)	(20,798)
FDIC insurance premium	3,283	2,507	3,318
Impact of the Tax Cuts and Jobs Act of 2017	0	0	(2,274)
Addition to reserve for uncertainties	0	31,123	0
Other, net	3,002	1,255	641
Income tax expense	$ 139,460	$ 147,002	$ 68,265