Description of Business, Basis of Presentation and Consolidation and Significant Accounting Policies - Recent Accounting Pronouncements - Income Taxes (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Non-current assets:
Other non-current assets	$ 11,452	$ 14,327	$ 42,915
Non-current liabilities:
Other long-term liabilities	$ 21,772	21,969	$ 31,959
Adjustment | Accounting Standards Update 2016-16
Non-current assets:
Other non-current assets		(28,588)
Non-current liabilities:
Other long-term liabilities		$ (9,990)