This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 35
-Paragraph 32
-URI http://asc.fasb.org/extlink&oid=121548190&loc=d3e32787-111569

+ Details

Name:	us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of investment in equity method investee and investment in and advance to affiliate.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- References

No definition available.

+ Details

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

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Purchases during the period (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=smp_FoshanGWOYNGSMPVehicleClimateControlCoolingProductsCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=smp_FoshanGuangdongAutomotiveAirConditioningCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=smp_FoshanCheYijiaNewEnergyTechnologyCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=smp_OrangeElectronicCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Aug. 31, 2019	Mar. 31, 2018	Nov. 30, 2017	Apr. 30, 2014	Jan. 31, 2013
Investments in and Advances to Affiliates, Balance [Abstract]
Investments in unconsolidated affiliates			$ 40,507	$ 38,858
Foshan GWOYNG SMP Vehicle Climate Control & Cooling Products Co. Ltd. [Member]
Investments in and Advances to Affiliates, Balance [Abstract]
Investments in unconsolidated affiliates			$ 18,869	18,099				$ 4,200		$ 14,000
Percentage of equity interest acquired			65.00%					15.00%		50.00%
Purchase price payment					$ 4,200
Purchases from equity method investment			$ 12,400	12,700
Foshan FGD SMP Automotive Compressor Co. Ltd [Member]
Investments in and Advances to Affiliates, Balance [Abstract]
Investments in unconsolidated affiliates			15,036	13,633					$ 12,500
Percentage of equity interest acquired									50.00%
Purchase price payment	$ 5,700					$ 6,800
Purchases from equity method investment			17,400	12,800
Foshan Che Yijia New Energy Technology Co., Ltd. [Member]
Investments in and Advances to Affiliates, Balance [Abstract]
Investments in unconsolidated affiliates			4,174	4,883			$ 5,100
Percentage of equity interest acquired							29.00%
Orange Electronic Co., Ltd [Member]
Investments in and Advances to Affiliates, Balance [Abstract]
Investments in unconsolidated affiliates			$ 2,428	2,243							$ 6,300
Percentage of equity interest acquired			19.40%								25.00%
Purchases from equity method investment			$ 4,400	$ 3,500
Impairment charge		$ 1,700			$ 1,700