Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (3,612)	$ (2,700)	$ (18,405)	$ (1,311)
Adjustments for changes in:
Foreign currency translation	(1,573)	(6,197)	(1,124)	(3,699)
Unrecognized employee benefit costs (including effects of foreign currency translation)	230	692	4,701	279
Fair value of cash flow hedges	(221)	(6)	47	(321)
Reclassification adjustments for items included in net loss:
Amortization of unrecognized employee benefit costs	(282)	64	(443)	194
Realized losses (gains) from settlement of cash flow hedges	4	(92)	123	(301)
Other comprehensive (loss) income	(1,842)	(5,539)	3,304	(3,848)
Comprehensive loss	(5,454)	(8,239)	(15,101)	(5,159)
Less: Comprehensive income attributable to noncontrolling interest	111	109	599	708
Comprehensive loss attributable to Ampco-Pittsburgh	$ (5,565)	$ (8,348)	$ (15,700)	$ (5,867)