Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (4,621)	$ (6,456)	$ (23,026)	$ (7,767)
Adjustments for changes in:
Foreign currency translation	(3,769)	(1,102)	(4,893)	(4,801)
Unrecognized employee benefit costs (including effects of foreign currency translation)	(9,551)	138	(4,850)	417
Fair value of cash flow hedges	(134)	(198)	(87)	(519)
Reclassification adjustments for items included in net loss:
Amortization of unrecognized employee benefit costs	156	(42)	(287)	152
Realized losses (gains) from settlement of cash flow hedges	53	46	176	(255)
Other comprehensive loss	(13,245)	(1,158)	(9,941)	(5,006)
Comprehensive loss	(17,866)	(7,614)	(32,967)	(12,773)
Less: Comprehensive income attributable to noncontrolling interest	188	440	787	1,148
Comprehensive loss attributable to Ampco-Pittsburgh	$ (18,054)	$ (8,054)	$ (33,754)	$ (13,921)