Mortgage Servicing Rights (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Expected amortization expense on mortgage servicing rights
2016	$ 750
2017	630
2018	530
2019	450
2020	380
Residential mortgage loans
Mortgage Servicing Rights
Unpaid principal balance	$ 798,510	$ 825,170	$ 839,260

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

No definition available.

Name:	srce_ServicingAssetAtAmortizedValueExpectedAmortizationAbstract
Namespace Prefix:	srce_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of expense to be charged against earnings in the next fiscal year following the latest balance sheet date, for the periodic recognition of servicing assets relative to estimated net servicing income.

+ References

No definition available.

+ Details

Name:	srce_ServicingAssetAtAmortizedValueExpectedAmortizationCurrent
Namespace Prefix:	srce_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of expense to be charged against earnings in the year five following the latest balance sheet date, for the periodic recognition of servicing assets relative to estimated net servicing income.

+ References

No definition available.

+ Details

Name:	srce_ServicingAssetAtAmortizedValueExpectedAmortizationInYearFive
Namespace Prefix:	srce_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of expense to be charged against earnings in the year four following the latest balance sheet date, for the periodic recognition of servicing assets relative to estimated net servicing income.

+ References

No definition available.

+ Details

Name:	srce_ServicingAssetAtAmortizedValueExpectedAmortizationInYearFour
Namespace Prefix:	srce_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of expense to be charged against earnings in the year three following the latest balance sheet date, for the periodic recognition of servicing assets relative to estimated net servicing income.

+ References

No definition available.

+ Details

Name:	srce_ServicingAssetAtAmortizedValueExpectedAmortizationInYearThree
Namespace Prefix:	srce_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of expense to be charged against earnings in the year two following the latest balance sheet date, for the periodic recognition of servicing assets relative to estimated net servicing income.

+ References

No definition available.

+ Details

Name:	srce_ServicingAssetAtAmortizedValueExpectedAmortizationInYearTwo
Namespace Prefix:	srce_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This is the result of the principal amount outstanding of total loans managed or securitized less securitized loans and loans that are in the process of being securitized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51814546&loc=d3e107314-111719

+ Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: