Bank Deposits (Scheduled Maturities of Certificates of Deposit) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deposits Liabilities Balance Sheet Reported Amounts [Abstract]
Within one year	$ 159	$ 2,719
One to three years	14	409
Three to five years		254
Certificates of deposit, less than $100,000	173	3,382
Within one year	20,098	63,650
One to three years	6,884	30,622
Certificates of deposit, $100,000 and greater	26,982	94,272
Total certificates of deposit	$ 27,155	$ 97,654

Time deposit maturities, less than one hundred thousand, next rolling twelve months.

No definition available.

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

- Definition

Time deposit maturities, less than one hundred thousand, over three rolling years.

+ References

No definition available.

+ Details

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

- Definition

Time deposit maturities, less than one hundred thousand, rolling years one to three.

+ References

No definition available.

+ Details

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

- Definition

Time deposit maturities, one hundred thousand or more, next rolling twelve months.

+ References

No definition available.

+ Details

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

- Definition

Time deposit maturities, one hundred thousand or more, rolling one to three years.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of time deposit liabilities, including certificates of deposit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=116652737&loc=d3e64164-112818

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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

- Definition

Amount of time deposit liabilities, including certificates of deposit, in denominations of $100,000 or more.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher SEC
-Name Industry Guide
-Number 3
-Section V
-Paragraph D-E

+ Details

Name:	us-gaap_TimeDeposits100000OrMore
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of time deposit liabilities, including certificates of deposit, in denominations of less than $100,000.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher SEC
-Name Industry Guide
-Number 3
-Section V
-Paragraph D-E

+ Details

Name:	us-gaap_TimeDepositsLessThan100000
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant