SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Purchased Credit-Impaired Loans (Details) - bulk_loan_acquisition	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Number of purchase transactions	1	7	0	5	3

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Number of Bulk Loan Acquisitions

No definition available.

Name:	banc_CertainLoansAcquiredinTransferNotAccountedforasDebtSecuritiesAcquiredDuringPeriodNumberofBulkLoanAcquisitions
Namespace Prefix:	banc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration