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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Present value of lessee's discounted obligation for lease payments from finance lease.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

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Including the current and noncurrent portions, the carrying value as of the balance sheet date of notes payable to banks, excluding mortgage notes, initially due beyond one year or beyond the operating cycle if longer.

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The carrying amount as of the balance sheet date for the aggregate of other miscellaneous borrowings owed by the reporting entity.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Carrying value as of the balance sheet date of uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

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Other Borrowings - Other Borrowings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2014
Debt Instrument [Line Items]
Lease liability	$ 11,813	$ 7,406
Other borrowings	252,787	243,685
Old National Bank
Debt Instrument [Line Items]
Other basis adjustments	428	517
Lease liability	11,813	7,406
Old National Bancorp
Debt Instrument [Line Items]
Other basis adjustments	(3,195)	(2,833)
Other borrowings	$ 213,246	223,762
Senior Unsecured Notes \| Old National Bancorp
Debt Instrument [Line Items]
Fixed rates	4.125%		4.125%
Senior unsecured notes (fixed rate 4.125%) maturing August 2024	$ 175,000	175,000	$ 175,000
Unamortized debt issuance costs related to senior unsecured notes	(559)	(715)
Junior Subordinated Debentures \| Old National Bancorp
Debt Instrument [Line Items]
Junior subordinated debentures (variable rates of 1.80% to 1.98%) maturing March 2035 to June 2037	$ 42,000	52,310
Subordinated Debt \| Old National Bank
Debt Instrument [Line Items]
Fixed rates	4.57%
Subordinated debentures (variable rate 4.57%)	$ 12,000	12,000
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 December 2052	$ 15,300	$ 0
Minimum \| Junior Subordinated Debentures \| Old National Bancorp
Debt Instrument [Line Items]
Variable rates	1.80%
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	1.98%
Maximum \| Leveraged Loans for NMTC \| Old National Bank
Debt Instrument [Line Items]
Fixed rates	1.43%