Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1,700	$ 600
Deferred Tax Assets, Gross, Noncurrent	0	(24,633)
Deferred tax assets:
Deferred compensation	13,684	22,325
Deferred income	2,381	2,015
Accrued expenses	13,683	11,652
Deferred Tax Assets, Operating Loss Carryforwards	189,644	222,065
Other	4,601	2,203
Gross deferred tax assets	223,993	260,260
Valuation allowance	(203,040)	(206,586)	$ (4,200)
Total deferred tax assets	20,953	53,674
Deferred tax liabilities:
Property and equipment	36,850	65,366
Basis difference in equity investments	2,346	5,715
Deferred Tax Liabilities, Gross	39,196	71,081
Deferred Tax Assets (Liabilities), Net [Abstract]
Deferred Tax Liabilities, Gross, Noncurrent	18,243	42,040
Deferred Tax Assets, Gross, Noncurrent	0	(24,633)
Total deferred tax liabilities	$ 18,243	$ 17,407