Other Borrowings - Other Borrowings (Details) - USD ($) $ in Thousands		12 Months Ended
	Nov. 01, 2017	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Lease liability		$ 20,955	$ 13,469
Other borrowings		764,870	743,003
Old National Bank
Debt Instrument [Line Items]
Other basis adjustments		97,872	89,588
Lease liability		20,955	13,469
Derivative collateralize position amount		97,600	88,000
Old National Bancorp
Debt Instrument [Line Items]
Other basis adjustments		18,207	23,363
Other borrowings		$ 479,759	484,759
Senior Unsecured Notes | Old National Bancorp
Debt Instrument [Line Items]
Fixed rates		4.125%
Senior unsecured notes (fixed rate 4.125%) maturing August 2024		$ 175,000	175,000
Unamortized debt issuance costs related to senior unsecured notes		$ (91)	(247)
Subordinated Debt | Old National Bank
Debt Instrument [Line Items]
Fixed rates		10.01%
Subordinated debentures		$ 12,000	12,000
Subordinated Debt | Old National Bank | SOFR
Debt Instrument [Line Items]
LIBOR rate	4.618%
Subordinated Debt | Old National Bancorp
Debt Instrument [Line Items]
Fixed rates		5.875%
Subordinated debentures		$ 150,000	150,000
Junior Subordinated Debentures | Old National Bancorp
Debt Instrument [Line Items]
Junior subordinated debentures (rates of 6.95% to 9.22%) maturing    July 2031 to September 2037		136,643	136,643
Leveraged Loans for NMTC | Old National Bank
Debt Instrument [Line Items]
Leveraged loans for NMTC (fixed rates of 1.00% to 1.43%) maturing December 2046 to June 2060		$ 154,284	$ 143,187
Minimum | Junior Subordinated Debentures | Old National Bancorp
Debt Instrument [Line Items]
Variable rates		6.95%
Minimum | Leveraged Loans for NMTC | Old National Bank
Debt Instrument [Line Items]
Fixed rates		1.00%
Maximum | Junior Subordinated Debentures | Old National Bancorp
Debt Instrument [Line Items]
Variable rates		9.22%
Maximum | Leveraged Loans for NMTC | Old National Bank
Debt Instrument [Line Items]
Fixed rates		1.43%