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Basis of Presentation (Details) | Jun. 30, 2018
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Basis of Presentation [Abstract] |
Equity ownership in entities included in consolidated financial statements, minimum | 50.00%

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- 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