Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Computed at the statutory rate	$ 13,880	$ 15,235	$ 41,731	$ 38,313
State income taxes, net of federal tax benefit	986	342	4,073	1,117
Discrete items related to ASU 2016-09	(31)	5	(2,567)	(1,372)
Tax exempt interest income	(833)	(955)	(2,292)	(3,160)
Tax exempt earnings on BOLI	(186)	(178)	(562)	(616)
Other differences, net	(2,914)	229	(1,732)	1,147
Provision for income taxes	$ 10,902	$ 14,678	$ 38,651	$ 35,429