Earnings per Share - Reconciliation of Net Income (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net income attributable to PQ Group Holdings Inc.	$ 25,252	$ 21,325	$ 19,245	$ 7,875	$ 25,435	$ (71,259)	$ (1,490)	$ (92,635)	$ 73,697	$ (139,949)	$ (278,771)
Denominator:
Weighted average shares outstanding – Basic (shares)	125,962,111	132,622,105	138,035,764	137,684,773	136,256,601	136,129,591	136,095,060	136,006,082	133,601,322	136,167,384	135,528,977
Weighted average shares outstanding – Diluted (shares)	127,538,343	134,096,839	139,149,560	138,749,065	137,528,028	137,354,427	136,095,060	136,006,082	135,088,172	137,708,931	136,450,953
Net income (loss) per share:
Basic income (loss) per share	$ 0.20	$ 0.16	$ 0.14	$ 0.06	$ 0.19	$ (0.52)	$ (0.01)	$ (0.68)	$ 0.55	$ (1.03)	$ (2.06)
Diluted income (loss) per share	0.20	0.16	0.14	0.06	0.18	(0.52)	(0.01)	(0.68)	0.55	(1.02)	(2.04)
Basic income per share—continuing operations	0.17	0.16	0.14	0.06	0.06	0.03	(0.06)	(0.02)	0.52	0.01	0.40
Diluted income per share—continuing operations	0.17	0.16	0.14	0.06	0.06	0.03	(0.06)	(0.02)	0.52	0.01	0.40
Basic income (loss) per share—discontinued operations	0.03	0	0	0	0.13	(0.56)	0.05	(0.66)	0.03	(1.04)	(2.46)
Diluted income (loss) per share—discontinued operations	$ 0.03	$ 0	$ 0	$ 0	$ 0.13	$ (0.55)	$ 0.05	$ (0.66)	$ 0.03	$ (1.03)	$ (2.44)