Income Taxes - Deferred Tax Assets Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 1,974,658	$ 1,826,656
Equity compensation	10,281	36,972
Deferred revenue	14,005	31,082
Tax credit and other attribute carryforwards	131,640	91,680
Insurance loss reserves	6,626	5,118
Accrued interest	234,033	357,285
Other	80,492	115,909
Subtotal	2,451,735	2,464,702
Valuation allowance	(1,869,490)	(1,807,728)
Deferred tax assets	582,245	656,974
Deferred tax liabilities:
Depreciation and amortization for tax in excess of book expense	146,448	288,088
Variable interest investments		641
Other	27,132	11,154
Deferred tax liability	173,580	299,883
Net deferred tax assets (liabilities)	408,665	357,091
Balance Sheet Summary :
Net noncurrent deferred tax asset (1)	419,003	366,586
Net noncurrent deferred tax liability	$ (10,338)	$ (9,495)