Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 1,238	$ (4,621)	$ 6,701	$ (23,026)
Adjustments for changes in:
Foreign currency translation	4,708	(3,769)	2,750	(4,893)
Unrecognized employee benefit costs (including effects of foreign currency translation)	(451)	(9,551)	147	(4,850)
Fair value of cash flow hedges	227	(134)	27	(87)
Reclassification adjustments for items included in net income (loss):
Amortization of unrecognized employee benefit costs	281	156	1,044	(287)
Realized losses from settlement of cash flow hedges	10	53	167	176
Other comprehensive income (loss)	4,775	(13,245)	4,135	(9,941)
Comprehensive income (loss)	6,013	(17,866)	10,836	(32,967)
Less: Comprehensive income attributable to noncontrolling interest	561	188	1,114	787
Comprehensive income (loss) attributable to Ampco-Pittsburgh	$ 5,452	$ (18,054)	$ 9,722	$ (33,754)