Acquisitions - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Jun. 01, 2021	Mar. 09, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Acquisition and integration related expenses			$ 2,916	$ 881	$ 10,934	$ 11,602
Depository Series A Shares
Business Acquisition [Line Items]
Preferred stock, fixed rate (as a percent)				7.00%
Preferred stock, conversion rate (as a percent)				2.50%
Old National Bancorp
Business Acquisition [Line Items]
Total combined assets	$ 45,000,000
Common stock, shares issued (in shares)	1.1336
Percentage of votes approved	99.00%
Consideration transferred	$ 6,500,000
Old National Bancorp | Depository Series A Shares
Business Acquisition [Line Items]
Preferred stock, fixed rate (as a percent)	7.00%
Preferred stock, conversion rate (as a percent)	2.50%
Bankmanagers Corporation
Business Acquisition [Line Items]
Common stock, shares issued (in shares)		4,930,231
Consideration transferred		$ 174,382
Total assets		1,150,905
Total deposits		950,076
Loans		$ 687,923
Fixed exchange ratio (in shares)		29.9675
Cash paid per share (in dollars per share)		$ 623.02
Special dividends paid (in dollars per share)		$ 346.00
Cash paid		$ 102,499
Goodwill		$ 59,649