LOANS AND ALLOWANCE FOR CREDIT LOSSES - Credit Quality Indicators Additional Information (Details)	9 Months Ended
Sep. 30, 2020
Receivables [Abstract]
Loans delinquent	60 days

Number of days delinquent at which a loan or lease is individually analyzed.

No definition available.

Name:	banc_FinancingReceivableDaysDelinquentClassifiedasCreditRisk
Namespace Prefix:	banc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration