Acquisition Activity (Narrative) (Details) (USD $)	0 Months Ended	12 Months Ended								0 Months Ended	12 Months Ended			12 Months Ended			12 Months Ended
	Dec. 02, 2011	Dec. 31, 2011	Dec. 31, 2010	Jul. 29, 2011	Jun. 30, 2011	Dec. 31, 2009	Dec. 31, 2011 Monroe Bancorp [Member]	Mar. 31, 2011 Monroe Bancorp [Member]	Dec. 31, 2010 Monroe Bancorp [Member]	Dec. 02, 2011 Integra [Member]	Dec. 31, 2011 Integra [Member]	Dec. 31, 2011 Minimum [Member]	Jul. 29, 2011 Minimum [Member]	Dec. 31, 2011 Minimum [Member] Integra [Member]	Dec. 31, 2011 Maximum [Member]	Jul. 29, 2011 Maximum [Member]	Dec. 31, 2011 Maximum [Member] Integra [Member]
Business Acquisition [Line Items]
Number of banking centers									15
Percentage of voting interest acquired									100.00%
Number of shares received per share for acquired company		1.90	7,600,000
Number of years for loss sharing provisions for commercial and single family residential mortgage loans													5			10
Number of years that loss recovery provisions are in effect from acquisition date												8			10
Number of branch locations		52								4
Value of shares received			$ 90,100,000
Goodwill		253,177,000	167,884,000	16,900,000		167,884,000		68,400,000
Goodwill deductible for income tax purposes		29,000,000
Purchase price											170,800,000
Deposits sold	106,900,000
Net gain on sale of deposit		500,000
Deposit premium		400,000
Time deposits related to divestiture		800,000
Accelerated amortization associated with core deposit intangible		700,000
Trust business assets under management approximate amount											328,000,000
Total assets under management by Old National's Wealth Management division		90,070,000					90,070,000				4,400,000,000
Cash transaction payments											1,300,000
Recorded acquisition-related costs											126,000
Customer relationship intangible assets		300,000			1,300,000			2,300,000			1,300,000
Core deposit intangible acquired, after tax				4,300,000
Loss sharing agreements amount, 80% on assets acquired											275,000,000
0% percent for losses on acquisition														275,000,000			467,200,000
Accelerated amortization of intangible assets, period in years		12
80% reimbursement for loss on acquisition											467,200,000
Estimated purchase price, allocated to net tangible assets acquired		11,200,000
Amount allocated to net definite-lived intangible assets		10,500,000
Transaction value		79,200,000
Full service banking centers servicing south central Indiana		17
Asset value of acquired company		$ 985,000,000									$ 1,827,350,000