Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Computed at the statutory rate	$ 17,539	$ 22,071	$ 53,719	$ 49,646
State income taxes, net of federal tax benefit	1,143	2,956	5,502	5,721
Tax exempt interest income	(1,752)	(1,105)	(4,594)	(3,090)
Tax exempt earnings on BOLI	(308)	(225)	(839)	(619)
Federal tax credits	(434)	(344)	(1,252)	(1,029)
Other differences, net	1,445	(78)	1,384	660
Actual tax provision	$ 17,633	$ 23,275	$ 53,920	$ 51,289