Segment Reporting (Schedule Of Operating Information, Segment) (Parenthetical) (Details)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Segment Reporting [Abstract]
Net revenues accounted for by individual client, maximum percentage	10.00%	10.00%

Net revenues accounted for by individual client, maximum percentage.

No definition available.

Name:	sf_NetRevenuesAccountedForByIndividualClientMaximumPercentage
Namespace Prefix:	sf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration