Capital lease obligation period.

No definition available.

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Balance Type:	na
Period Type:	duration

- Definition

Long-term capital lease term.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Long-term capital lease renewal option term.

+ References

No definition available.

+ Details

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Namespace Prefix:	onb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of renewal options available for long-term capital lease.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The reference rate for the variable rate of the lessor's capital lease (sales-type and direct financing leases), such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ 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)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

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

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Aggregate par or stated value of issued nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable preferred shares, par value and other disclosure concepts are in another section within stockholders' equity.

+ 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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.

+ 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)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Balance Type:
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- Details

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- Details

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Other Borrowings - Additional Information (Detail) $ in Millions						3 Months Ended
	May 01, 2016	Dec. 31, 2006 USD ($)	Sep. 30, 2006 USD ($)	Dec. 31, 2005 USD ($)	Jan. 01, 2004 Item	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Aug. 31, 2014 USD ($)	Mar. 31, 2007 USD ($)	Jul. 31, 2006 USD ($)	Mar. 31, 2005 USD ($)
Debt Instrument [Line Items]
Preferred securities
Long-term capital lease obligation period, in years					25 years
Long-term capital lease obligation renewal period, in years					10 years
Number of renewal option for 10 years period \| Item					1
St Joseph Capital Trust II [Member]
Debt Instrument [Line Items]
Preferred securities												$ 5.0
Reference rate of the variable interest rate for preferred securities						Three-month London Interbank Offered Rate ("LIBOR") plus 175 basis points
Home Federal Statutory Trust I [Member]
Debt Instrument [Line Items]
Preferred securities			$ 15.0
Reference rate of the variable interest rate for preferred securities						Three-month LIBOR plus 165 basis points
Tower Capital Trust 2 [Member]
Debt Instrument [Line Items]
Preferred securities				$ 8.0
Reference rate of the variable interest rate for preferred securities						Three-month LIBOR plus 134 basis points
Tower Capital Trust 3 [Member]
Debt Instrument [Line Items]
Preferred securities		$ 9.0
Reference rate of the variable interest rate for preferred securities						Three-month LIBOR plus 169 basis points
Anchor BanCorp Wisconsin Inc [Member]
Debt Instrument [Line Items]
Capital lease obligation period	5 years
Junior Subordinated Debt [Member] \| St Joseph Capital Trust II [Member] \| Trust Preferred Securities [Member]
Debt Instrument [Line Items]
Maturity date						Mar. 17, 2035
LIBOR rate						1.75%
Junior Subordinated Debt [Member] \| Home Federal Statutory Trust I [Member] \| Trust Preferred Securities [Member]
Debt Instrument [Line Items]
LIBOR rate			1.65%
Junior Subordinated Debt [Member] \| Tower Capital Trust 2 [Member] \| Trust Preferred Securities [Member]
Debt Instrument [Line Items]
LIBOR rate				1.34%
Junior Subordinated Debt [Member] \| Tower Capital Trust 3 [Member] \| Trust Preferred Securities [Member]
Debt Instrument [Line Items]
LIBOR rate		1.69%
Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Senior unsecured notes									$ 175.0
Fixed rates									4.125%
Maturity date						Aug. 15, 2024
Monroe Bancorp Capital Trust I [Member]
Debt Instrument [Line Items]
Preferred securities											$ 3.0
Reference rate of the variable interest rate for preferred securities						Three-month LIBOR plus 160 basis points
Monroe Bancorp Capital Trust I [Member] \| Junior Subordinated Debt [Member] \| Trust Preferred Securities [Member]
Debt Instrument [Line Items]
LIBOR rate						1.60%
Monroe Bancorp Statutory Trust II [Member]
Debt Instrument [Line Items]
Preferred securities										$ 5.0
Reference rate of the variable interest rate for preferred securities						Three-month LIBOR plus 160 basis points
Monroe Bancorp Statutory Trust II [Member] \| Junior Subordinated Debt [Member] \| Trust Preferred Securities [Member]
Debt Instrument [Line Items]
LIBOR rate						1.60%