Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Computed at the statutory rate	$ 12,620	$ 13,708
State income taxes, net of federal tax benefit	1,345	1,822
Discrete items related to ASU 2016-09	(26)	(273)
Tax exempt interest income	(961)	(677)
Tax exempt earnings on BOLI	(179)	(186)
Federal tax credits	(729)	0
Other differences, net	328	(428)
Provision for income taxes	$ 12,398	$ 13,966