Litigation - Schedule of Loss Contingencies by Contingency (Parenthetical) (Detail) - Claim	Sep. 30, 2019	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Number of claims inactive or transferred to MDL panel	729	678

Number of inactive claims or claims classified at MDL.

No definition available.

Name:	ap_ClaimsClassifiedInVariousJurisdictionsAsInactiveOrTransferredToStateOrFederalJudicialPanelOnMultiDistrictLitigation
Namespace Prefix:	ap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant