Long term capital lease obligation period.

No definition available.

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Namespace Prefix:	onb_
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Balance Type:	na
Period Type:	duration

- Definition

Long term capital lease obligation renewal period.

+ References

No definition available.

+ Details

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

- Definition

Percentage of borrowings collateralized by investment securities and residential real estate loans.

+ References

No definition available.

+ Details

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- Definition

Renewal option in ten year span.

+ References

No definition available.

+ Details

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- 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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- 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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- Details

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- 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 SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: 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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- Definition

The calculated weighted average interest rate for Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13(3)(a))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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- 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

+ Details

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- 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 SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 3: 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

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29

-Article 5

+ Details

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Balance Type:	credit
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- 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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ 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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Financing Activities - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	0 Months Ended
	Mar. 31, 2015 Item	Sep. 30, 2006	Dec. 31, 2005	Dec. 31, 2006	Dec. 31, 2014	Mar. 31, 2014	Aug. 31, 2014	Mar. 31, 2005	Jul. 31, 2006	Mar. 31, 2007
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	1onb_RenewalOptionInTenYearSpan
Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Senior unsecured notes							175,000
Fixed rate							4.125%
Maturity date	Aug. 15, 2024
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Weighted-average rates of Federal Home Loan Bank advances	0.87%				0.77%
Percentage of borrowings collateralized by investment securities and residential real estate loans	149.00%
St Joseph Capital Trust II [Member]
Debt Instrument [Line Items]
Maturity date	Mar. 17, 2035
Preferred securities								5,000
Reference rate of the variable interest rate for preferred securities	Three-month LIBOR plus 175 basis points
LIBOR rate	1.75%
Monroe Bancorp Capital Trust I [Member]
Debt Instrument [Line Items]
Preferred securities									3,000
Monroe Bancorp Statutory Trust II [Member]
Debt Instrument [Line Items]
Preferred securities										5,000
Reference rate of the variable interest rate for preferred securities	Three-month LIBOR plus 160 basis points
LIBOR rate	1.60%
Home Federal Statutory Trust I [Member]
Debt Instrument [Line Items]
Preferred securities		15,000
Reference rate of the variable interest rate for preferred securities	Three-month LIBOR plus 165 basis points
LIBOR rate		1.65%
Tower Capital Trust 2 [Member]
Debt Instrument [Line Items]
Preferred securities			8,000
Reference rate of the variable interest rate for preferred securities	Three-month LIBOR plus 134 basis points
LIBOR rate			1.34%
Tower Capital Trust 3 [Member]
Debt Instrument [Line Items]
Preferred securities				$ 9,000
Reference rate of the variable interest rate for preferred securities	Three-month LIBOR plus 169 basis
LIBOR rate				1.69%