Accumulated Other Comprehensive Loss - Line Items Affected on Condensed Consolidated Statements of Operations for Components Reclassified from Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net sales (foreign currency sales contracts)	$ 103,516	$ 63,578
Depreciation and amortization (foreign currency purchase contracts)	(5,922)	(3,925)
Costs of products sold (excluding depreciation and amortization)	(84,663)	(51,105)
Selling and administrative	(15,298)	(13,508)
Other income (expense)	(1,082)	1,164
Income tax provision	(135)	850
Net loss attributable to Ampco-Pittsburgh shareholders	(4,783)	(2,890)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] | Amortization of Unrecognized Employee Benefit Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Costs of products sold (excluding depreciation and amortization)	(15)	725
Selling and administrative	582	323
Other income (expense)	166	140
Total before income tax	733	1,188
Income tax provision	0	(403)
Net loss attributable to Ampco-Pittsburgh shareholders	733	785
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] | Realized Gains from Sale of Marketable Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Selling and administrative	(6)	(46)
Income tax provision	0	16
Net loss attributable to Ampco-Pittsburgh shareholders	(6)	(30)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] | Realized Gains/Losses from Settlement of Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net sales (foreign currency sales contracts)	0	(10)
Depreciation and amortization (foreign currency purchase contracts)	(7)	(7)
Costs of products sold (excluding depreciation and amortization)	(148)	236
Total before income tax	(155)	219
Income tax provision	0	(84)
Net loss attributable to Ampco-Pittsburgh shareholders	$ (155)	$ 135