XML 15 R101.htm IDEA: XBRL DOCUMENT v3.19.2

BUSINESS SEGMENTS - Additional Information (Detail) - Segment	1 Months Ended	6 Months Ended
	Aug. 31, 2018	Jun. 30, 2019
Segment Reporting Information [Line Items]
Number of reportable segments		3
Mariner Finance, LLC [Member]
Segment Reporting Information [Line Items]
Stock purchase agreement, stock sold, percentage	100.00%

X

- Definition

Stock Purchase Agreement, Stock Sold, Percentage

+ References

No definition available.

+ Details

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

X

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- 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

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

X

- Details

Name:	srt_CounterpartyNameAxis=fnb_MarinerFinanceLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: