-- None. No documentation exists for this element. --

No definition available.

Name:	source_FinancingReceivableModificationsSubsequentPaymentDefaultAbstract
Namespace Prefix:	source_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the threshold period of time used to determine if a modified loan is in default or transferred to nonaccrual.

+ References

No definition available.

+ Details

Name:	source_FinancingReceivableModificationsSubsequentPaymentDefaultPeriodPastDue
Namespace Prefix:	source_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

+ Details

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

- Definition

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953682-111524

+ Details

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

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_InterestRateBelowMarketReductionMember
Namespace Prefix:
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Balance Type:
Period Type:

Loan and Lease Financings (Details 4) $ in Thousands	3 Months Ended
Loan and Lease Financings (Details 4) $ in Thousands	Mar. 31, 2021 USD ($) default item	Mar. 31, 2020 default item	Dec. 31, 2020 USD ($)
Loans and leases classified as TDR
Number of Modifications \| item	0	0
Number of Defaults \| default	0	1
Loans and leases classified as troubled debt restructuring	$ 9,686		$ 11,486
Troubled debt restructured loans and leases which had payment defaults within twelve months following modification
Default threshold	90 days
Performing
Loans and leases classified as TDR
Loans and leases classified as troubled debt restructuring	$ 327		330
Nonperforming
Loans and leases classified as TDR
Loans and leases classified as troubled debt restructuring	$ 9,359		$ 11,156
Interest Rate Below Market Reduction [Member]
Loans and leases classified as TDR
Number of Modifications \| item	0	0