Federal Home Loan Bank Advances - Summary of FHLB Advances (Parenthetical) (Detail) - Old National Bank [Member] - Federal Home Loan Bank Advances [Member]	6 Months Ended
Jun. 30, 2017
Federal Home Loan Bank, Advances [Line Items]
Maturity, Start date	Jul. 31, 2017
Maturity, End date	Apr. 30, 2027
Minimum [Member]
Federal Home Loan Bank, Advances [Line Items]
Fixed rates	0.96%
Variable rates	1.09%
Maximum [Member]
Federal Home Loan Bank, Advances [Line Items]
Fixed rates	6.08%
Variable rates	1.33%

Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Earliest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

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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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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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