Acquisitions and FDIC Indemnification Asset (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Loans	$ 23,535	$ 27,754
Foreclosed Assets	630	720
Total Covered Assets	24,165	28,474
ASC 310-30 Loans [Member]
Loans	3,071	4,279
Foreclosed Assets	0	0
Total Covered Assets	3,071	4,279
Non ASC 310-30 Loans [Member]
Loans	20,464	23,475
Foreclosed Assets	0	0
Total Covered Assets	20,464	23,475
Other Assets [Member]
Loans	0	0
Foreclosed Assets	630	720
Total Covered Assets	$ 630	$ 720

Represents the carrying amount of all categories of financing receivables held in portfolio and assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance, whose losses will be shared with the Federal Deposit Insurance Corporation under the loss-sharing agreement.

No definition available.

Name:	thff_CoveredAssets
Namespace Prefix:	thff_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant