Income Taxes - Schedule of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 24,300	$ 40,300	$ 26,700
State	5,000	5,900	4,500
Total current	29,300	46,200	31,200
Deferred:
Federal	18,400	2,900	11,100
State	2,500	500	1,400
Total deferred	20,917	3,369	12,449
Total income tax expense	$ 50,201	$ 49,623	$ 43,662