Parent Company Financial Statements (Statement Of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income	$ 72,460	$ 38,214	$ 13,737
Depreciation	9,674	8,990	8,853
Net premium (discount) on investment securities	12,135	7,590	2,188
Stock option expense	3,436	2,369	1,310
(Increase) decrease in other assets	26,161	16,797	(44,008)
(Decrease) increase in other liabilities	12,276	(17,995)	(6,212)
Total adjustments	71,286	58,296	26,559
Net cash flows provided by operating activities	143,746	96,510	40,296
Purchases of investment securities available-for-sale	(550,934)	(1,106,040)	(2,274,090)
Proceeds from sales of investment securities available-for-sale	545,995	481,471	1,042,138
Purchases of premises and equipment and other assets	(11,486)	(7,460)	(13,944)
Net cash flows provided by (used in) investing activities	1,005,313	436,568	601,585
Payments related to retirement of debt	(211,228)	(279,649)	(133,949)
Cash dividends paid on common stock	(26,513)	(24,361)	(30,380)
Cash dividends paid on preferred stock	0	0	(1,514)
Common stock repurchased	(1,526)	(705)	(353)
Common stock reissued under stock option, restricted stock and stock purchase plans	140	12	97
Common stock issued	222	197	197,756
Net cash flows used in financing activities	(1,177,739)	(778,802)	(337,617)
Net increase (decrease) in cash and cash equivalents	(28,680)	(245,724)	304,264
Cash and cash equivalents at beginning of period	251,552	497,276	193,012
Cash and cash equivalents at end of period	222,872	251,552	497,276
Old National Bancorp [Member]
Net income	72,460	38,214	13,737
Depreciation	31	49	67
Net premium (discount) on investment securities	0	0	434
Net securities (gains) losses	(20)	0	(663)
Stock option expense	129	253	392
Restricted stock expense	3,307	2,116	918
(Increase) decrease in other assets	(4,927)	13,064	(6,302)
(Decrease) increase in other liabilities	3,628	(3,414)	2,450
Equity in undistributed earnings of affiliates	58,422	22,019	0
Dividends received from affiliates in excess of earnings	0	0	69,626
Total adjustments	(56,274)	(9,951)	66,922
Net cash flows provided by operating activities	16,186	28,263	80,659
Cash and cash equivalents of acquisitions	447	0	0
Transfer subsidiary from parent to bank subsidiary	0	791	0
Purchases of investment securities available-for-sale	1,081	(500)	(191,994)
Proceeds from sales of investment securities available-for-sale	0	0	192,222
Net payments from (advances to) affiliates	18,886	150,852	(145,989)
Purchases of premises and equipment and other assets	0	(7)	0
Net cash flows provided by (used in) investing activities	20,414	151,136	(145,761)
Payments related to retirement of debt	0	(150,000)	0
Cash dividends paid on common stock	(26,513)	(24,361)	(30,380)
Cash dividends paid on preferred stock	0	0	(1,514)
Common stock repurchased	(1,526)	(705)	(353)
Repurchase of TARP preferred stock and warrants	0	0	(101,200)
Common stock reissued under stock option, restricted stock and stock purchase plans	140	12	97
Common stock issued	222	197	197,756
Net cash flows used in financing activities	(27,677)	(174,857)	64,406
Net increase (decrease) in cash and cash equivalents	8,923	4,542	(696)
Cash and cash equivalents at beginning of period	26,653	22,111	22,807
Cash and cash equivalents at end of period	$ 35,576	$ 26,653	$ 22,111