Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 1,389	$ (4,662)
Adjustments for changes in:
Foreign currency translation	2,498	2,252
Unrecognized employee benefit costs (including effects of foreign currency translation)	(413)	(255)
Unrealized holding gains on marketable securities	0	185
Fair value of cash flow hedges	(315)	224
Reclassification adjustments for items included in net income (loss):
Amortization of unrecognized employee benefit costs	130	733
Realized gains from sale of marketable securities	0	(6)
Realized gains from settlement of cash flow hedges	(209)	(155)
Other comprehensive income	1,691	2,978
Comprehensive income (loss)	3,080	(1,684)
Less: Comprehensive income attributable to noncontrolling interest	599	124
Comprehensive income (loss) attributable to Ampco-Pittsburgh	$ 2,481	$ (1,808)