Parent Company Financial Statements (Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Trading securities - at fair value	$ 2,816	$ 0
Investment securities-available for sale	2,071,276	1,960,222
Other assets	229,469	189,419
Total assets	8,609,683	7,263,892	8,005,335
Other liabilities	248,941	202,019
Other borrowings	290,774	421,911
Shareholders' equity	1,033,556	878,805	843,826	730,865
Total liabilities and shareholders' equity	8,609,683	7,263,892
Old National Bancorp [Member]
Deposits in affiliate bank	35,576	26,653
Trading securities - at fair value	2,816	0
Investment securities-available for sale	1,204	976
Investment in affiliates, Banking subsidiaries	915,041	703,949
Investment in affiliates, Non-Banks	43,314	45,330
Advances to affiliates	0	45,177
Other assets	86,861	83,026
Total assets	1,084,812	905,111
Other liabilities	25,258	18,342
Other borrowings	25,998	7,964
Shareholders' equity	1,033,556	878,805
Total liabilities and shareholders' equity	$ 1,084,812	$ 905,111