Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (1,466)	$ 1,238	$ 72	$ 6,701
Adjustments for changes in:
Foreign currency translation	(2,499)	4,708	(2,041)	2,750
Unrecognized employee benefit costs (including effects of foreign currency translation)	275	(451)	247	147
Fair value of cash flow hedges	(8)	227	547	27
Reclassification adjustments for items included in net (loss) income:
Amortization of unrecognized employee benefit costs	457	281	1,371	1,044
Settlements of cash flow hedges	(304)	10	(1,024)	167
Other comprehensive (loss) income	(2,079)	4,775	(900)	4,135
Comprehensive (loss) income	(3,545)	6,013	(828)	10,836
Less: Comprehensive income attributable to noncontrolling interest	124	561	534	1,114
Comprehensive (loss) income attributable to Ampco-Pittsburgh	$ (3,669)	$ 5,452	$ (1,362)	$ 9,722