Income Taxes - Reconciliation of Tax Expense at Effective Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate reconciliation, at federal statutory income tax rate	35.00%	35.00%	35.00%
Income Tax Expense, Continuing Operations Income Tax Reconciliation [Abstract]
Tax expense at the statutory tax rate	$ 50,841	$ 45,660	$ 45,365
Increase (decrease) in tax resulting from:
Tax-exempt income	(4,374)	(4,092)	(4,255)
State income tax, net of federal income tax benefit	4,301	3,791	3,541
Income Tax Credits and Adjustments	(2,128)	(2,249)	(313)
Other, net	983	552	876
Total income tax expense	$ 49,623	$ 43,662	$ 45,214