Loans at Acquisition Date [Line Items]

No definition available.

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- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the best estimate at the acquisition date of the contractual cash flows not expected to be collected, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

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

- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the fair value of the receivables acquired, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

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

- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the gross contractual amounts receivable, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

Name:	us-gaap_BusinessCombinationAcquiredReceivablesGrossContractualAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=onb_FoundersMember
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- Details

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Data Type:	na
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- Details

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- Details

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Acquisition and Divestiture Activity - Schedule of Acquired Loan Data (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	May 01, 2016	Dec. 31, 2015
Founders Financial Corporation [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date			$ 339,569
Founders Financial Corporation [Member] \| Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	$ 6,607
Gross Contractual Amounts Receivable at Acquisition Date	11,103
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	2,684
Founders Financial Corporation [Member] \| Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	332,962
Gross Contractual Amounts Receivable at Acquisition Date	439,031
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	61,113
Anchor BanCorp Wisconsin Inc [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date		$ 1,636,605
Anchor BanCorp Wisconsin Inc [Member] \| Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	20,174
Gross Contractual Amounts Receivable at Acquisition Date	29,544
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	6,153
Anchor BanCorp Wisconsin Inc [Member] \| Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	1,616,431
Gross Contractual Amounts Receivable at Acquisition Date	2,143,532
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	$ 274,155