Significant Accounting Policies - Other Long-Term Liabilities (Details)	9 Months Ended
Oct. 07, 2018
Significant Accounting Policies
Other long-term liabilities weighted average amortization (in years)	14 years

Represents the weighted average amortization period of leasehold interests.

No definition available.

Name:	sfs_WeightedAverageAmortizationPeriodLeaseholdInterests
Namespace Prefix:	sfs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration