v3.26.3
Accumulated Other Comprehensive Loss - Net Change and Ending Balances for Various Components of Accumulated Other Comprehensive Loss (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning Balance $ 48,294 $ 76,495 $ 47,963 $ 71,091
Net change 26 (632) (693) 9,125
Ending Balance 50,063 74,559 50,063 74,559
Foreign Currency Translation [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning Balance     863 (27,691)
Net change     (240) 10,232
Ending Balance 623 (17,459) 623 (17,459)
Unrecognized Employee Benefit Costs [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning Balance     (29,405) (39,856)
Net change     (330) (1,343)
Ending Balance (29,735) (41,199) (29,735) (41,199)
Cash Flow Hedges [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning Balance     116 (102)
Net change     (123) 236
Ending Balance (7) 134 (7) 134
Less: Noncontrolling Interest [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning Balance     (222) (813)
Net change     707 333
Ending Balance 485 (480) 485 (480)
Accumulated Other Comprehensive Loss Attributable to Ampco-Pittsburgh [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning Balance     (28,204) (66,836)
Net change     (1,400) 8,792
Ending Balance (29,604) (58,044) (29,604) (58,044)
Total Accumulated Other Comprehensive Loss [Member]        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning Balance     (28,426) (67,649)
Net change     (693) 9,125
Ending Balance $ (29,119) $ (58,524) $ (29,119) $ (58,524)