Document and Entity Information	9 Months Ended
	Sep. 30, 2019 shares
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	ONB
Security Exchange Name	NASDAQ
Entity Registrant Name	Old National Bancorp /IN/
Entity Central Index Key	0000707179
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock
Entity Common Stock, Shares Outstanding	170,031,000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	1-15817
Entity Incorporation, State or Country Code	IN
Entity Tax Identification Number	35-1539838
Entity Address, Address Line One	One Main Street
Entity Address, City or Town	Evansville
Entity Address, State or Province	IN
Entity Address, Postal Zip Code	47708
City Area Code	800
Local Phone Number	731-2265
Document Quarterly Report	true
Document Transition Report	false