Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Computed at the statutory rate	$ 17,172	$ 20,560
State income taxes, net of federal tax benefit	1,890	2,063
Stock-based compensation	103	26
Tax exempt interest income	(2,510)	(1,421)
Tax exempt earnings on BOLI	(241)	(319)
Federal tax credits	(590)	(1,034)
Other differences, net	(1,461)	819
Actual tax provision	$ 14,363	$ 20,694