Recently Issued Accounting Guidance (Narrative) (Details) - USD ($) $ in Millions	Jan. 01, 2016	Dec. 31, 2015
Prospective Adoption Of New Accounting Pronouncements [Abstract]
Impact of reduction in both other assets and senior notes	$ 9.6
Impact of reduction in both total assets and liabilities		$ 9.9

New accounting pronouncement or change in accounting principle impact of reduction in both other assets and senior notes.

No definition available.

Name:	sf_NewAccountingPronouncementOrChangeInAccountingPrincipleImpactOfReductionInBothOtherAssetsAndSeniorNotes
Namespace Prefix:	sf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant