Income Taxes Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current tax expense:
Federal	$ 33,872	$ 34,455	$ 32,957
State	1,698	2,042	1,126
Total	35,570	36,497	34,083
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal	7,968	12,752	18,523
State	3,086	672	0
Total	11,054	13,424	18,523
Income tax expense	$ 46,624	$ 49,921	$ 52,606