Loans and Leases Receivable, Increase (Decrease) in Number of Loans

No definition available.

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

- Definition

Loans and Leases Receivable, Net Of Deferred Income, Increase (Decrease) in Period

+ References

No definition available.

+ Details

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

- Definition

Loans and Leases Receivable, Net Of Deferred Income, Percentage Increase (Decrease) in Period

+ References

No definition available.

+ Details

Name:	banc_LoansandLeasesReceivableNetOfDeferredIncomePercentageIncreaseDecreaseinPeriod
Namespace Prefix:	banc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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

- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

+ Details

Name:	us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Indicates the number of mortgages under each classification.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.3)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

+ Details

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

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=banc_LoansAndFinanceReceivablesNonTraditionalMortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis=us-gaap_FirstMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=banc_GreenLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=banc_LoanPortfolioConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=banc_NonTraditionalSingleFamilyResidentialMortgageGreenLoansFirstLienPortfolioMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditScoreFicoAxis=banc_FICOScoreGreaterthanEightHundredMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditScoreFicoAxis=banc_FICOScoreSevenHundredtoSevenHundredNinetyNineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditScoreFicoAxis=us-gaap_FicoScore600To699Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditScoreFicoAxis=banc_FICOScoreLessthanSixHundredMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditScoreFicoAxis=banc_NoFICOScoreAvailableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

LOANS AND LEASES AND ALLOWANCE FOR LOAN AND LEASE LOSSES - Non Traditional Mortgage Performance by Credit Score (Detail) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($) Loan	Dec. 31, 2016 USD ($) Loan	Sep. 30, 2016 USD ($)
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 6,226,897	$ 6,034,752	$ 6,568,791
Non-Traditional Mortgages (NTM)
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 793,946	$ 885,148
Consumer \| Non-Traditional Mortgages (NTM)
Financing Receivable, Recorded Investment [Line Items]
Count \| Loan	579	663
Loans	$ 793,946	$ 885,148
Amount change	$ (91,200)
Percent Change	(10.30%)
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans (HELOC) - first liens
Financing Receivable, Recorded Investment [Line Items]
Count \| Loan	567	651
Loans	$ 790,388	$ 881,589
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 85,800	$ 91,000
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens
Financing Receivable, Recorded Investment [Line Items]
Count \| Loan	101	107
Loans	$ 82,289	$ 87,469
Count Change \| Loan	0
Amount change	$ 0
Percent Change	0.00%
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Recorded Investment [Line Items]
Concentration risk percentage	100.00%
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| Greater than 800
Financing Receivable, Recorded Investment [Line Items]
Count \| Loan	12	15
Loans	$ 8,410	$ 9,139
Count Change \| Loan	(3)
Amount change	$ (729)
Percent Change	(0.90%)
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| Greater than 800 \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Recorded Investment [Line Items]
Concentration risk percentage	10.20%	11.10%
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| 700-799
Financing Receivable, Recorded Investment [Line Items]
Count \| Loan	58	50
Loans	$ 43,168	$ 38,567
Count Change \| Loan	8
Amount change	$ 4,601
Percent Change	5.70%
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| 700-799 \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Recorded Investment [Line Items]
Concentration risk percentage	52.50%	46.80%
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| 600-699
Financing Receivable, Recorded Investment [Line Items]
Count \| Loan	24	28
Loans	$ 22,479	$ 27,384
Count Change \| Loan	(4)
Amount change	$ (4,905)
Percent Change	(6.00%)
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| 600-699 \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Recorded Investment [Line Items]
Concentration risk percentage	27.30%	33.30%
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| Less than 600
Financing Receivable, Recorded Investment [Line Items]
Count \| Loan	3	1
Loans	$ 4,329	$ 1,800
Count Change \| Loan	2
Amount change	$ 2,529
Percent Change	3.10%
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| Less than 600 \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Recorded Investment [Line Items]
Concentration risk percentage	5.30%	2.20%
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| No FICO
Financing Receivable, Recorded Investment [Line Items]
Count \| Loan	4	7
Loans	$ 3,903	$ 5,399
Count Change \| Loan	(3)
Amount change	$ (1,496)
Percent Change	(1.90%)
Consumer \| Non-Traditional Mortgages (NTM) \| Green Loans \| Green Loans (HELOC) - first liens \| No FICO \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Recorded Investment [Line Items]
Concentration risk percentage	4.70%	6.60%