Fair Value Measurements (Details 5) - Non-recurring - USD ($) $ in Thousands	3 Months Ended
Jun. 30, 2015	Dec. 31, 2014
Impaired loans
Fair value measurements
Impairment charges (recoveries)	$ 0
Partnership investments
Fair value measurements
Impairment charges (recoveries)	0
Mortgage servicing rights
Fair value measurements
Impairment charges (recoveries)	0
Repossessions
Fair value measurements
Impairment charges (recoveries)	0
Other real estate
Fair value measurements
Impairment charges (recoveries)	10
Total
Fair value measurements
Impaired loans - collateral based	4,178	$ 1,007
Assets measured at fair value	16,209	13,974
Total \| Partnership investments
Fair value measurements
Accrued income and other assets	1,010	1,343
Total \| Mortgage servicing rights
Fair value measurements
Accrued income and other assets	4,661	4,733
Total \| Repossessions
Fair value measurements
Accrued income and other assets	5,433	5,156
Total \| Other real estate
Fair value measurements
Accrued income and other assets	927	1,735
Level 3
Fair value measurements
Impaired loans - collateral based	4,178	1,007
Assets measured at fair value	16,209	13,974
Level 3 \| Partnership investments
Fair value measurements
Accrued income and other assets	1,010	1,343
Level 3 \| Mortgage servicing rights
Fair value measurements
Accrued income and other assets	4,661	4,733
Level 3 \| Repossessions
Fair value measurements
Accrued income and other assets	5,433	5,156
Level 3 \| Other real estate
Fair value measurements
Accrued income and other assets	$ 927	$ 1,735

Represents the portion of the accrued income and other assets balance sheet assertion valued at fair value.

No definition available.

Name:	srce_AccruedIncomeAndOtherAssetsFairValueDisclosure
Namespace Prefix:	srce_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents impaired loans receivable based on the fair value of the underlying collateral if repayment is expected solely from the collateral as presented on the statement of financial position which are due the Company as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	srce_ImpairedLoansReceivableFairValueDisclosure
Namespace Prefix:	srce_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=51824106&loc=d3e2420-110228

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

+ Details

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

- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

No definition available.

+ Details

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

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

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=srce_ImpairedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=srce_PartnershipInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=srce_MortgageServicingRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=srce_RepossessionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=srce_OtherRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: