Parent Company Financial Statements (Statements Of Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net securities gains									$ 15,052	$ 8,691	$ 17,124
Interest on borrowings	8,039	8,622	9,291	9,990	9,640	14,577	14,553	14,950	35,942	53,720	78,432
Other expense									14,004	14,253	11,377
Income before income taxes and equity in undistributed earnings of affiliates	34,029	25,598	38,095	30,063	31,026	24,842	22,943	20,951	127,785	99,762	43,480
Income tax expense	11,020	5,861	10,889	8,340	8,812	8,045	5,927	4,518	36,110	27,302	5,266
Net income	23,009	19,737	27,206	21,723	22,214	16,797	17,016	16,433	91,675	72,460	38,214
Old National Bancorp [Member]
Dividends from affiliates									53,042	19,670	27,744
Net securities gains									165	20	0
Other income									1,710	1,372	1,020
Other income (loss) from affiliates									153	(1)	435
Total income									55,070	21,061	29,199
Interest on borrowings									786	1,270	9,165
Other expense									14,270	9,572	11,672
Total expense									15,056	10,842	20,837
Income before income taxes and equity in undistributed earnings of affiliates									40,014	10,219	8,362
Income tax expense									(5,909)	(3,819)	(7,833)
Income before equity in undistributed earnings of affiliates									45,923	14,038	16,195
Equity in undistributed earnings of affiliates									45,752	58,422	22,019
Net income									$ 91,675	$ 72,460	$ 38,214