Label	Element	Value
Private Capital [Member]
Proceeds from Issuance of Private Placement	us-gaap_ProceedsFromIssuanceOfPrivatePlacement	$ 382,900,000
Additional Paid-in Capital [Member] | Private Capital [Member]
Proceeds from Issuance of Private Placement	us-gaap_ProceedsFromIssuanceOfPrivatePlacement	382,575,000
Preferred Stock [Member]
Proceeds from Issuance Initial Public Offering	us-gaap_ProceedsFromIssuanceInitialPublicOffering	$ 498,516,000
Nonvoting Common Stock Equivalents [Member] | Common Stock [Member]
Common Stock, Shares, Issued	us-gaap_CommonStockSharesIssued	10,829,990
Nonvoting Common Stock Equivalents [Member] | Common Stock [Member] | Private Capital [Member]
Proceeds from Issuance of Private Placement	us-gaap_ProceedsFromIssuanceOfPrivatePlacement	$ 108,000
Common Stock, Shares, Issued	us-gaap_CommonStockSharesIssued	10,829,990
Voting Common Stock [Member]
Common Stock, Shares, Outstanding	us-gaap_CommonStockSharesOutstanding	77,786,716
Common Stock, Shares, Outstanding	us-gaap_CommonStockSharesOutstanding	78,555,290
Voting Common Stock [Member] | Common Stock [Member] | Private Capital [Member]
Proceeds from Issuance of Private Placement	us-gaap_ProceedsFromIssuanceOfPrivatePlacement	$ 217,000
Common Stock, Shares, Issued	us-gaap_CommonStockSharesIssued	21,690,334
Civic Acquisition [Member]
Business Combination, Cash Consideration	banc_BusinessCombinationCashConsideration	$ (160,420,000)
Liabilities	us-gaap_Liabilities	147,577,000
Assets	us-gaap_Assets	307,997,000
Homeowners Association Services Divison [Member]
Business Combination, Cash Consideration	banc_BusinessCombinationCashConsideration	237,798,000
Liabilities	us-gaap_Liabilities	4,125,095,000
Assets	us-gaap_Assets	4,362,893,000
Pacific Western Bank [Member]
Liabilities	us-gaap_Liabilities	7,742,473,000
Proceeds from Issuance of Common Stock	us-gaap_ProceedsFromIssuanceOfCommonStock	663,004,000
Pacific Western Bank [Member] | Additional Paid-in Capital [Member]
Proceeds from Issuance of Common Stock	us-gaap_ProceedsFromIssuanceOfCommonStock	$ 662,869,000
Pacific Western Bank [Member] | Class B Nonvoting [Member] | Common Stock [Member]
Common Stock, Shares, Issued	us-gaap_CommonStockSharesIssued	477,321
Proceeds from Issuance of Common Stock	us-gaap_ProceedsFromIssuanceOfCommonStock	$ 5,000
Pacific Western Bank [Member] | Voting Common Stock [Member] | Common Stock [Member]
Common Stock, Shares, Issued	us-gaap_CommonStockSharesIssued	57,157,632
Proceeds from Issuance of Common Stock	us-gaap_ProceedsFromIssuanceOfCommonStock	$ 130,000
Restricted Stock-Based Compensation Surrendered [Member] | Voting Common Stock [Member] | Common Stock [Member]
Common Stock, Shares, Issued	us-gaap_CommonStockSharesIssued	130,735
Restricted Stock-Based Compensation [Member] | Voting Common Stock [Member] | Common Stock [Member]
Common Stock, Shares, Issued	us-gaap_CommonStockSharesIssued	899,309