Income Taxes - Deferred Tax Assets Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 1,967,910	$ 1,974,658
Equity compensation	7,038	10,281
Deferred revenue	16,494	14,005
Tax credit and other attribute carryforwards	100,752	131,640
Insurance loss reserves	2,451	6,626
Accrued interest	206,088	234,033
Other	82,167	80,492
Subtotal	2,382,900	2,451,735
Valuation allowance	(1,917,390)	(1,869,490)
Deferred tax assets	465,510	582,245
Deferred tax liabilities:
Depreciation and amortization for tax in excess of book expense	102,810	146,448
Other	23,920	27,132
Deferred tax liability	126,730	173,580
Net deferred tax assets (liabilities)	338,780	408,665
Balance Sheet Summary :
Net noncurrent deferred tax asset (1)	345,091	419,003
Net noncurrent deferred tax liability	$ (6,311)	$ (10,338)