Parent Company Financial Statements - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets
Equity securities, at fair value	$ 80,372	$ 52,507
Investment in affiliates:
Goodwill	1,998,716	1,998,716	$ 1,036,994	$ 1,036,994
Total assets	49,089,836	46,763,372
Liabilities and Shareholders’ Equity
Other borrowings	764,870	743,003
Shareholders’ equity	5,562,900	5,128,595	$ 3,012,018	$ 2,972,656
Total liabilities and shareholders’ equity	49,089,836	46,763,372
Old National Bancorp
Assets
Deposits in affiliate bank	284,294	418,959
Equity securities, at fair value	51,241	30,717
Investment securities - available-for-sale	15,886	16,814
Investment in affiliates:
Banking subsidiaries	5,530,637	5,000,153
Non-banks	44,395	44,938
Goodwill	59,506	59,506
Accrued interest receivable and other assets	127,540	135,025
Total assets	6,113,499	5,706,112
Liabilities and Shareholders’ Equity
Other liabilities	70,840	92,758
Other borrowings	479,759	484,759
Shareholders’ equity	5,562,900	5,128,595
Total liabilities and shareholders’ equity	$ 6,113,499	$ 5,706,112