Supplemental Guarantors Consolidating Condensed Financial Information - (Statement of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ (2,122)	$ (6,344)	$ (9,636)	$ (13,379)	$ 4,118	$ (5,443)	$ (9,235)	$ (13,864)	$ (31,481)	$ (24,424)	$ (109,990)
Foreign currency translation adjustments									7,526	3,190	(21,211)
Comprehensive income (loss)									(23,955)	(21,234)	(131,201)
Consolidation, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									3,634	(496)	84,762
Foreign currency translation adjustments									111	85	138
Comprehensive income (loss)									3,745	(411)	84,900
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									(31,481)	(24,424)	(109,990)
Foreign currency translation adjustments									0	0	0
Comprehensive income (loss)									(31,481)	(24,424)	(109,990)
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									(9,102)	(486)	(76,908)
Foreign currency translation adjustments									0	0	0
Comprehensive income (loss)									(9,102)	(486)	(76,908)
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									5,468	982	(7,854)
Foreign currency translation adjustments									7,415	3,105	(21,349)
Comprehensive income (loss)									$ 12,883	$ 4,087	$ (29,203)