Fair Value Measurements (Details 5) (Non-recurring, USD $)	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Impaired loans
Fair value measurements
Impairment charges (recoveries)	$ 0
Partnership investments
Fair value measurements
Impairment charges (recoveries)	(30,000)
Mortgage servicing rights
Fair value measurements
Impairment charges (recoveries)	0
Repossessions
Fair value measurements
Impairment charges (recoveries)	620,000
Other real estate
Fair value measurements
Impairment charges (recoveries)	0
Total
Fair value measurements
Impaired loans - collateral based	3,471,000	1,007,000
Assets measured at fair value	15,196,000	13,974,000
Total \| Partnership investments
Fair value measurements
Accrued income and other assets	1,010,000	1,343,000
Total \| Mortgage servicing rights
Fair value measurements
Accrued income and other assets	4,590,000	4,733,000
Total \| Repossessions
Fair value measurements
Accrued income and other assets	4,607,000	5,156,000
Total \| Other real estate
Fair value measurements
Accrued income and other assets	1,518,000	1,735,000
Level 3
Fair value measurements
Impaired loans - collateral based	3,471,000	1,007,000
Assets measured at fair value	15,196,000	13,974,000
Level 3 \| Partnership investments
Fair value measurements
Accrued income and other assets	1,010,000	1,343,000
Level 3 \| Mortgage servicing rights
Fair value measurements
Accrued income and other assets	4,590,000	4,733,000
Level 3 \| Repossessions
Fair value measurements
Accrued income and other assets	4,607,000	5,156,000
Level 3 \| Other real estate
Fair value measurements
Accrued income and other assets	$ 1,518,000	$ 1,735,000

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 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: 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=8077374&loc=d3e2420-110228

+ 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

- Details

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