Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Computed at the statutory rate	$ 14,955	$ 14,143	$ 27,575	$ 27,851
State income taxes, net of federal tax benefit	1,420	1,265	2,765	3,087
Tax exempt interest income	(1,024)	(782)	(1,985)	(1,459)
Tax exempt earnings on BOLI	(215)	(190)	(394)	(376)
Federal tax credits	(729)	0	(1,458)	0
Other differences, net	1,209	(653)	1,511	(1,354)
Provision for income taxes	$ 15,616	$ 13,783	$ 28,014	$ 27,749