Contingent Liabilities, Commitments, and Financial Instruments with Off-Balance-Sheet Risk (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Investments in tax-advantaged and other operating partnerships	$ 23,760	$ 11,140
Tax-advantaged and other operating partnerships commitment	$ 15,710	$ 4,950

Amount of commitment or contingent commitments to tax-advantaged and other operating partnerships.

No definition available.

Name:	srce_TaxAdvantagedAndOtherOperatingPartnershipsCommitment
Namespace Prefix:	srce_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant