Name:	fnb_AssumptionForFairValueOnSecuritizationDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesAnnualizedConstantPrepaymentRate
Namespace Prefix:	fnb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of zero point five zero percent adverse change in prepayment speed.

No definition available.

Name:	fnb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfZeroPointFiveZeroPercentAdverseChangeInPrepaymentSpeed
Namespace Prefix:	fnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of zero point five zero percent favorable change in prepayment speed.

No definition available.

Name:	fnb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfZeroPointFiveZeroPercentFavorableChangeInPrepaymentSpeed
Namespace Prefix:	fnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of zero point two five percent adverse change in prepayment speed.

No definition available.

Name:	fnb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfZeroPointTwoFivePercentAdverseChangeInPrepaymentSpeed
Namespace Prefix:	fnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of zero point two five percent favorable change in prepayment speed.

No definition available.

Name:	fnb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfZeroPointTwoFivePercentFavorableChangeInPrepaymentSpeed
Namespace Prefix:	fnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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.

No definition available.

Name:	us-gaap_AssumptionForFairValueAsOfBalanceSheetDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Discount rate which is used to value residual cash flows generated by financial assets of the securitization, asset-backed financing arrangement, or similar transfer for initial fair value measurement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107207-111719

Name:	us-gaap_AssumptionForFairValueOnSecuritizationDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Weighted average life of securitized assets for initial fair value measurement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107207-111719

Name:	us-gaap_FairValueAssumptionDateOfSecuritizationOrAssetBackedFinancingArrangementTransferorsContinuingInvolvementServicingAssetsOrLiabilitiesWeightedAverageLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The hypothetical financial impact of a 10 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107314-111719

Name:	us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

Name:	us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInPrepaymentSpeed
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The hypothetical financial impact of a 20 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

Name:	us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.