Acquisition and Divestiture Activity - Schedule of Preliminary Purchase Price Allocation (Detail) (USD $) In Thousands, unless otherwise specified					6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2013 Indiana Community Bancorp [Member]
Loans At Acquisition Date [Line Items]
Cash and cash equivalents					$ 78,540
Investment securities-available for sale					147,710
Federal Home Loan Bank stock, at cost	40,584	37,927	30,835		7,092
Loans	5,126,904	5,141,831	4,660,870		497,434
Premises and equipment					13,345
Accrued interest receivable					2,165
Other real estate owned					6,111
Company-owned life insurance					15,833
Other assets					49,655
Deposits	(6,840,093)	(7,278,953)	(6,670,273)		(784,589)
Other borrowings					(15,464)
Accrued expenses and other liabilities					(18,564)
Net tangible assets acquired					(732)
Definite-lived intangible assets acquired					3,024
Goodwill	339,382	338,820	253,177	253,177	86,205
Purchase price					$ 88,497