Debt instrument, principal amount sold pursuant to over-allotment option.

No definition available.

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

- Definition

Number of types of subsequent events.

+ References

No definition available.

+ Details

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Namespace Prefix:	sf_
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Balance Type:	na
Period Type:	duration

- Definition

Redemption price, percentage of principal amount.

+ References

No definition available.

+ Details

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

- Definition

Date when the business acquisition agreement was executed, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionDateOfAcquisitionAgreement1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=sf_ZieglerWealthManagementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=sf_SeniorNotes520DueOctober2047Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Events (Details)			9 Months Ended
Subsequent Events (Details)	Oct. 30, 2017	Oct. 04, 2017 USD ($)	Sep. 30, 2017 USD ($) item	Oct. 27, 2017 USD ($)	Dec. 31, 2016 USD ($)
Subsequent Event [Line Items]
Number of types of subsequent events \| item			2
Long-term Debt			$ 796,609,000		$ 795,891,000
Stated interest rate			4.25%
Debt instrument, maturity date			Dec. 31, 2024
Subsequent Event [Member] \| Ziegler Wealth Management [Member]
Subsequent Event [Line Items]
Business acquisition, definitive agreement entered date	Oct. 30, 2017
Subsequent Event [Member] \| Senior Notes 5.20% due October 2047 [Member]
Subsequent Event [Line Items]
Long-term Debt		$ 200,000,000
Stated interest rate		5.20%
Debt instrument, maturity date		Oct. 31, 2047
Redemption price for on or after October 15, 2022, percentage of principal amount		100.00%
Debt instrument, principal amount sold pursuant to over-allotment option				$ 25,000,000