Income Taxes - Rate reconcilation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income tax expense at the statutory rate	$ 22,906	$ 36,863	$ 22,179
Provision to return and deferred tax adjustments	1,858	145	1,705
State tax, net of federal benefit	3,584	3,504	2,717
Permanent adjustments	1,514	1,810	173
Tax rate in excess of (less than) statutory tax rates	8,161	(5,035)	(985)
Impact of Finance Structure	(8,165)
Gain on divestiture		3,465
Nondeductible transaction costs	3,844
Other	316	(773)	338
Subtotal	34,018	39,979	26,127
Change in valuation allowance	(7,396)	(637)	2,047
Total income tax (benefit) expense	$ 26,622	$ 39,342	$ 28,174
Statutory tax rate	20.00%	35.00%	35.00%
Deferred Tax Asset Fixed Assets [Member]
Release of deferred tax asset	$ 8,200