Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Computed at the statutory rate	$ 15,620	$ 14,955	$ 36,180	$ 27,575
State income taxes, net of federal tax benefit	2,296	1,420	4,359	2,765
Discrete items related to ASU 2016-09	43	(81)	69	(107)
Tax exempt interest income	(1,421)	(1,024)	(2,842)	(1,985)
Tax exempt earnings on BOLI	(212)	(215)	(531)	(394)
Federal tax credits	(1,034)	(729)	(2,068)	(1,458)
Other differences, net	301	1,290	1,120	1,618
Provision for income taxes	$ 15,593	$ 15,616	$ 36,287	$ 28,014