Sale of Receivables (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Sale of Receivables [Abstract]
Sale of receivables to financial institutions	$ 190.0	$ 184.1	$ 361.0	$ 341.6
Charge related to sale of receivables	$ 6.4	$ 6.3	$ 12.1	$ 11.7

The amount of charges incurred relating to the sale of receivables during the reporting period.

No definition available.

Name:	smp_SaleOfReceivablesRelatedCharges
Namespace Prefix:	smp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration