Long-Term Debt - Loss on Extinguishment of Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Extinguishment of Debt [Line Items]
Loss on extinguishment of debt	$ 3,565	$ 0	$ 212
Write-off of previously unamortized debt issuance costs	2,065	$ 0	$ 212
2015 Facilities
Extinguishment of Debt [Line Items]
Loss on extinguishment of debt	3,600
Write-off of previously unamortized debt issuance costs	2,100
Write off of lender fees	$ 1,500