Cover	3 Months Ended
	Mar. 31, 2022 shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	001-15817
Entity Registrant Name	Old National Bancorp
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
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	292,959,000
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Entity Central Index Key	0000707179
Current Fiscal Year End Date	--12-31
Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Common stock, no par value
Trading Symbol	ONB
Security Exchange Name	NASDAQ
Depositary Shares, each representing a 1/40th interest in a share of Non-Cumulative Perpetual Preferred Stock, Series A
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/40th interest in a share of Non-Cumulative Perpetual Preferred Stock, Series A
Trading Symbol	ONBPP
Security Exchange Name	NASDAQ
Depositary Shares, each representing a 1/40th interest in a share of Non-Cumulative Perpetual Preferred Stock, Series C
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/40th interest in a share of Non-Cumulative Perpetual Preferred Stock, Series C
Trading Symbol	ONBPO
Security Exchange Name	NASDAQ