Significant Accounting Policies - Cash and Cash Equivalents (Details)	9 Months Ended
Oct. 07, 2018
Significant Accounting Policies
Maximum processing period credit card, debit card and electronic transfer transactions to be classified as cash and cash equivalents	7 days

Represents the maximum duration of the processing time for credit card, debit card and electronic benefits transfer transactions to be classified as cash and cash equivalents.

No definition available.

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