Parent Company Financial Statements (Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Trading securities - at fair value	$ 3,097	$ 2,816
Total investment securities - available-for-sale	2,500,784	2,071,276
Other assets	236,888	209,321
Total assets	9,543,623	8,609,683	7,263,892
Other liabilities	242,797	248,941
Other borrowings	237,493	290,774
Shareholders' equity	1,194,565	1,033,556	878,805	843,826
Total liabilities and shareholders' equity	9,543,623	8,609,683
Old National Bancorp [Member]
Deposits in affiliate bank	39,262	35,576
Trading securities - at fair value	3,097	2,816
Total investment securities - available-for-sale	1,826	1,204
Investment in affiliates, Banking subsidiaries	1,073,721	915,041
Investment in affiliates, Non-Banks	43,067	43,314
Other assets	85,540	86,861
Total assets	1,246,513	1,084,812
Other liabilities	27,287	25,258
Other borrowings	24,661	25,998
Shareholders' equity	1,194,565	1,033,556
Total liabilities and shareholders' equity	$ 1,246,513	$ 1,084,812