Accumulated Other Comprehensive Loss - Line Items Affected on Consolidated Statements of Operations for Components Reclassified from Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Depreciation and amortization (foreign currency purchase contracts)	$ (4,226)	$ (5,368)	$ (8,484)	$ (10,004)
Costs of products sold (excluding depreciation and amortization) (futures contracts - copper and aluminum)	(80,675)	(91,981)	(167,430)	(174,085)
Income (loss) before income taxes	2,826	(6,128)	3,261	(4,178)
Other loss - net	545	(225)	1,141	601
Income tax effect	(677)	(592)	(1,262)	(651)
Net income (loss) attributable to Ampco-Pittsburgh	1,489	(7,335)	622	(6,193)
Amortization of Unrecognized Employee Benefit Costs [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other loss - net	(164)	(258)	(231)	(323)
Net income (loss) attributable to Ampco-Pittsburgh	(101)	(281)	(169)	(340)
Settlements of Cash Flow Hedges [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Depreciation and amortization (foreign currency purchase contracts)	(7)	(8)	(13)	(14)
Costs of products sold (excluding depreciation and amortization) (futures contracts - copper and aluminum)	(99)	(281)	(163)	(336)
Income (loss) before income taxes	(106)	(289)	(176)	(350)
Income tax effect	5	8	7	10
Net income (loss) attributable to Ampco-Pittsburgh	$ (164)	$ (258)	$ (231)	$ (323)