Accumulated Other Comprehensive Loss - Net Change and Ending Balances for Various Components of 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
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 47,576	$ 77,670	$ 47,963	$ 71,091
Net change	(190)	5,375	(719)	9,757
Ending Balance	48,294	76,495	48,294	76,495
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			863	(27,691)
Net change			(406)	10,702
Ending Balance	457	(16,989)	457	(16,989)
Unrecognized Employee Benefit Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(29,405)	(39,856)
Net change			(220)	(1,403)
Ending Balance	(29,625)	(41,259)	(29,625)	(41,259)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			116	(102)
Net change			(93)	458
Ending Balance	23	356	23	356
Less: Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(222)	(813)
Net change			477	240
Ending Balance	255	(573)	255	(573)
Accumulated Other Comprehensive Loss Attributable to Ampco-Pittsburgh [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(28,204)	(66,836)
Net change			(1,196)	9,517
Ending Balance	(29,400)	(57,319)	(29,400)	(57,319)
Total Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(28,426)	(67,649)
Net change			(719)	9,757
Ending Balance	$ (29,145)	$ (57,892)	$ (29,145)	$ (57,892)