Income Taxes - The components of the net deferred income tax asset (liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 22, 2017
Deferred tax assets:
Depreciation and amortization	$ 7,354	$ 10,210
Deferred revenue	1,808	2,115
Net operating loss carryforwards	50,353	74,656
Alternative minimum tax credit carryforward	167	2,523	$ 2,500
Accrued expenses and other	2,328	7,891
Total deferred tax assets	62,010	97,395
Deferred tax liabilities:
Depreciation and amortization	(1,785)	(3,315)
Intangible assets	(189)	(487)
Deferred expenses and other	(129)	(138)
Total deferred tax liabilities	(2,103)	(3,940)
Valuation allowance:
Beginning balance	(95,412)	(88,737)
Decrease (increase) during the period	34,349	(6,675)
Total valuation allowance	(61,063)	(95,412)
Net deferred tax asset (liability)	(1,156)	(1,957)
Deferred income tax asset	203	257
Deferred income tax liability	$ (1,359)	$ (2,214)