Income Taxes - Reconciliation of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax benefit at U.S. statutory rate	$ 205,777	$ 139,657	$ 192,390
Impact of the Tax Act	114,716	0	0
State taxes, net of federal income tax	24,891	11,788	18,323
Tax credits	1,908	6,163	3,937
Valuation allowance	(246,037)	(142,862)	(111,797)
Goodwill impairment	(78,515)	(10,789)	(7,856)
Stock compensation	(4,093)	(5,716)	0
Other, net	(851)	(1,831)	(1,626)
Meals and entertainment	(726)	(868)	(1,090)
Return to provision	(555)	(920)	(72)
Total	$ 16,515	$ (5,378)	$ 92,209