Acquisition of KBW, Inc. (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended
Feb. 15, 2013	Mar. 31, 2013
Business Acquisition [Line Items]
Fair value of awards issued as retention		$ 30.6
KBW [Member]
Business Acquisition [Line Items]
Cash consideration per share	$ 8.00
Cash consideration per share before extraordinary dividend amount	$ 10.00
Extraordinary dividend	$ 2.00
Stock consideration, common stock	0.2143%
Goodwill recorded in business combination	307.9
Transaction costs		$ 9.8
KBW [Member] \| Common Stock [Member]
Business Acquisition [Line Items]
Shares issued	6.7
KBW [Member] \| Restricted Awards [Member]
Business Acquisition [Line Items]
Shares issued	2.2

Business acquisition, acquiree oustanding stock right to receive acquirer common stock

No definition available.

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

- Definition

Business acquisition, acquiree oustanding stock right to receive, cash consideration per share

+ References

No definition available.

+ Details

Name:	sf_BusinessAcquisitionAcquireeOustandingStockRightToReceiveCashConsiderationPerShare
Namespace Prefix:	sf_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Business acquisition, acquiree oustanding stock right to receive, cash consideration per share before extraordinary dividend amount

+ References

No definition available.

+ Details

Name:	sf_BusinessAcquisitionAcquireeOustandingStockRightToReceiveCashConsiderationPerShareBeforeExtraordinaryDividendAmount
Namespace Prefix:	sf_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Business acquisition, acquiree oustanding stock right to receive, cash consideration per share, extraordinary dividend

+ References

No definition available.

+ Details

Name:	sf_BusinessAcquisitionAcquireeOustandingStockRightToReceiveCashConsiderationPerShareExtraordinaryDividend
Namespace Prefix:	sf_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Restricted stock or unit expense.

+ References

No definition available.

+ Details

Name:	sf_RestrictedStockOrUnitExpense
Namespace Prefix:	sf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of shares of equity interests issued or issuable to acquire entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of goodwill arising from a business combination, which is the excess of the cost of the acquired entity over the amounts assigned to assets acquired and liabilities assumed.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 52

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 53

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=21917927&loc=d3e1043-128460

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 59

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration