LOANS AND LEASES AND ALLOWANCE FOR LOAN AND LEASE LOSSES - Summary of Loans Purchased and Sold (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017 USD ($) bulk_loan_acquisition	Sep. 30, 2016 USD ($) bulk_loan_acquisition	Sep. 30, 2017 USD ($) bulk_loan_acquisition	Sep. 30, 2016 USD ($) bulk_loan_acquisition
Receivables [Abstract]
Number of purchase transactions \| bulk_loan_acquisition	0	1	0	1
Total unpaid principal balance of purchased PCI loans at acquisition	$ 0	$ 103,799	$ 0	$ 103,799
Total fair value of purchased PCI loans at acquisition	$ 0	$ 90,984	$ 0	$ 90,984

Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Acquired During Period, Unpaid Principal Balance With Credit Quality Deterioration At Acquisition

No definition available.

Name:	banc_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodUnpaidPrincipalBalanceWithCreditQualityDeteriorationAtAcquisition
Namespace Prefix:	banc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration