CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (3,016)	$ (9,606)	$ (7,001)	$ (89,685)
Other comprehensive income (loss), net of tax:
Pension and postretirement benefits	(20)	162	(223)	486
Net (loss) gain from hedging activities	(301)	201	(3,326)	1,302
Foreign currency translation	18,850	1,286	60,492	(7,919)
Total other comprehensive income (loss)	18,529	1,649	56,943	(6,131)
Comprehensive income (loss)	15,513	(7,957)	49,942	(95,816)
Less: Comprehensive income (loss) attributable to noncontrolling interests	82	(165)	661	(165)
Comprehensive income (loss) attributable to PQ Group Holdings Inc.	$ 15,431	$ (7,792)	$ 49,281	$ (95,651)