Loans and Leases (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	$ 80,190	$ 27,646	$ 101,878
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	7,500	8,100
Financing Receivable, Nonaccrual	91,163	92,353
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	36,523	11,085
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due	12,232	9,788
Unfunded Commitments For Troubled Debt Restructurings	900	1,200
Financing Receivable, Troubled Debt Restructuring, Postmodification	37,441	27,663	90,373
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	209,400
Loans and Leases Receivable, Gross	19,153,357	18,910,740
Commercial Portfolio Segment [Member]
Business Acquisition [Line Items]
Financing Receivable, Nonaccrual	44,902	70,672
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	6,894	4,164
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due	2,863	2,800
Loans and Leases Receivable, Gross	7,534,801	7,714,358
Finance Receivable, Payroll Protection Program Loan \| Commercial Portfolio Segment [Member]
Business Acquisition [Line Items]
Loans and Leases Receivable, Gross	1,100,000
Asset Based [Member] \| Commercial Portfolio Segment [Member]
Business Acquisition [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification	17,008	3,082	28,947
Financing Receivable, Nonaccrual	2,679	30,162
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	2,128	0
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due	0	19
Financing Receivable, Troubled Debt Restructuring, Postmodification	$ 1,741	3,082	$ 33,947
Credit Concentration Risk [Member]
Business Acquisition [Line Items]
Concentration Risk, Percentage	59.00%
Financing Receivable, Nonaccrual	$ 53,400
Nonaccrual [Member]
Business Acquisition [Line Items]
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	36,500	11,100
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due	3,400	1,200
Financing Receivable Recorded Investment Nonaccrual Status Current	$ 51,300	$ 80,000

Financing Receivable Recorded Investment Nonaccrual Status Current

No definition available.

Name:	pacw_FinancingReceivableRecordedInvestmentNonaccrualStatusCurrent
Namespace Prefix:	pacw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing receivable recorded investment 30 to 89 days past due.

+ References

No definition available.

+ Details

Name:	pacw_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
Namespace Prefix:	pacw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due - replaces Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due

+ References

No definition available.

+ Details

Name:	pacw_LoanReceivableRecordedInvestmentEqualtoGreaterthan90DaysPastDue
Namespace Prefix:	pacw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unfunded Commitments For Troubled Debt Restructurings.

+ References

No definition available.

+ Details

Name:	pacw_UnfundedCommitmentsForTroubledDebtRestructurings
Namespace Prefix:	pacw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13531-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13537-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

+ Details

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

- Definition

Amount of increase (decrease) in allowance for credit loss on financing receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919249-210447

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919258-210447

+ Details

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

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

+ Details

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

- Definition

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18794-111554

+ Details

Name:	us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=pacw_FinanceReceivablePayrollProtectionProgramLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	pacw_CommercialCollateralizedFinancingReceivableLoanTypeAxis=pacw_AssetBasedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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