Fair Value Measurements (Details) $ in Thousands	3 Months Ended
Mar. 31, 2023 USD ($) Party	Dec. 31, 2022 USD ($)
Fair Value, Net Asset (Liability) [Abstract]
Number of independent third parties \| Party	2
Fair Value [Member] \| LEVEL 1 [Member]
Fair Value, Net Asset (Liability) [Abstract]
Cash and cash equivalents	$ 24,196	$ 21,150
Deferred compensation	22,410	20,190
Short term borrowings	57,614	55,031
Long-term debt	215,487	184,589
Fair Value [Member] \| LEVEL 2 [Member]
Fair Value, Net Asset (Liability) [Abstract]
Cash flow interest rate swap	3,311	5,174
Carrying Amount [Member] \| LEVEL 1 [Member]
Fair Value, Net Asset (Liability) [Abstract]
Cash and cash equivalents	24,196	21,150
Deferred compensation	22,410	20,190
Short term borrowings	57,614	55,031
Long-term debt	215,487	184,589
Carrying Amount [Member] \| LEVEL 2 [Member]
Fair Value, Net Asset (Liability) [Abstract]
Cash flow interest rate swap	$ 3,311	$ 5,174

Fair value portion of currency related to deferred compensation.

No definition available.

Name:	smp_DeferredCompensationFairValue
Namespace Prefix:	smp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The number of independent third parties from whom cash flow interest rate swap agreement obtained.

+ References

No definition available.

+ Details

Name:	smp_NumberOfIndependentThirdParties
Namespace Prefix:	smp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

+ Details

Name:	us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Fair value as of the balance sheet date of all interest rate derivative assets designated as cash flow hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624163-113959

+ Details

Name:	us-gaap_InterestRateCashFlowHedgeAssetAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_ShorttermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: