Income Taxes - Balance Sheet Classification of Net Deferred Income Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Noncurrent assets	$ 2,518	$ 10,731
Noncurrent liabilities	(13,707)	(60,018)
Net deferred income tax asset (liability)	$ (11,189)	$ (49,287)