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Basis of Presentation (Details)	Mar. 31, 2019
Basis of Presentation [Abstract]
Equity ownership in entities included in consolidated financial statements, minimum	50.00%

X

- Definition

The threshold equity ownership percentage in the entities included in the consolidated financial statements.

+ References

No definition available.

+ Details

Name:	smp_EquityOwnershipInEntitiesIncludedInConsolidatedFinancialStatementsThreshold
Namespace Prefix:	smp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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- References

No definition available.

+ Details

Name:	us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration