Loans and Leases (Details 10) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	$ 138,785	$ 132,472
Allowance for Loan and Lease Losses, Write-offs	(93,589)	(32,262)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	6,368	15,575
Allowance for Loan and Lease Losses Write-offs, Net	(87,221)	16,687
Provision for Loan and Lease Losses	293,000	23,000
Loans and Leases Receivable, Allowance, ending balance	348,181	138,785
Financing Receivable, Individually Evaluated for Impairment	3,659	6,197
Financing Receivable, Collectively Evaluated for Impairment	344,522	132,588
Financing Receivable, Individually Evaluated for Impairment	133,076	99,546
Financing Receivable, Collectively Evaluated for Impairment	18,950,301	18,747,326
Loans held for investment, net	19,083,377	18,846,872
Previously Reported
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	138,785
Loans and Leases Receivable, Allowance, ending balance		138,785
Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	3,617
Loans and Leases Receivable, Allowance, ending balance		3,617
Mortgages [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance		46,021
Allowance for Loan and Lease Losses, Write-offs	(10,686)	(997)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	617	983
Allowance for Loan and Lease Losses Write-offs, Net	10,069	14
Provision for Loan and Lease Losses	98,528	(1,432)
Loans and Leases Receivable, Allowance, ending balance	138,342
Financing Receivable, Individually Evaluated for Impairment	237	231
Financing Receivable, Collectively Evaluated for Impairment	138,105	44,344
Financing Receivable, Individually Evaluated for Impairment	50,139	28,038
Financing Receivable, Collectively Evaluated for Impairment	7,849,797	7,944,709
Loans held for investment, net	7,899,936	7,972,747
Mortgages [Member] \| Previously Reported
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	44,575
Loans and Leases Receivable, Allowance, ending balance		44,575
Mortgages [Member] \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	5,308
Loans and Leases Receivable, Allowance, ending balance		5,308
Real Estate Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance		28,209
Allowance for Loan and Lease Losses, Write-offs	0	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	21	0
Allowance for Loan and Lease Losses Write-offs, Net	(21)	0
Provision for Loan and Lease Losses	56,383	2,335
Loans and Leases Receivable, Allowance, ending balance	78,356
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	78,356	30,544
Financing Receivable, Individually Evaluated for Impairment	1,766	1,834
Financing Receivable, Collectively Evaluated for Impairment	3,358,515	2,735,968
Loans held for investment, net	3,360,281	2,737,802
Real Estate Construction [Member] \| Previously Reported
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	30,544
Loans and Leases Receivable, Allowance, ending balance		30,544
Real Estate Construction [Member] \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	(8,592)
Loans and Leases Receivable, Allowance, ending balance		(8,592)
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance		56,360
Allowance for Loan and Lease Losses, Write-offs	(82,105)	(30,426)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	5,529	14,397
Allowance for Loan and Lease Losses Write-offs, Net	76,576	16,029
Provision for Loan and Lease Losses	134,591	21,197
Loans and Leases Receivable, Allowance, ending balance	126,403
Financing Receivable, Individually Evaluated for Impairment	3,422	5,966
Financing Receivable, Collectively Evaluated for Impairment	122,981	55,562
Financing Receivable, Individually Evaluated for Impairment	81,171	69,674
Financing Receivable, Collectively Evaluated for Impairment	7,421,734	7,625,822
Loans held for investment, net	7,502,905	7,695,496
Commercial Portfolio Segment [Member] \| Previously Reported
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	61,528
Loans and Leases Receivable, Allowance, ending balance		61,528
Commercial Portfolio Segment [Member] \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	6,860
Loans and Leases Receivable, Allowance, ending balance		6,860
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance		1,882
Allowance for Loan and Lease Losses, Write-offs	(798)	(839)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	201	195
Allowance for Loan and Lease Losses Write-offs, Net	597	644
Provision for Loan and Lease Losses	3,498	900
Loans and Leases Receivable, Allowance, ending balance	5,080
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	5,080	2,138
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	320,255	440,827
Loans held for investment, net	320,255	440,827
Consumer Portfolio Segment [Member] \| Previously Reported
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	2,138
Loans and Leases Receivable, Allowance, ending balance		2,138
Consumer Portfolio Segment [Member] \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	41
Loans and Leases Receivable, Allowance, ending balance		41
Non Purchased Credit Impaired Loans and Leases
Allowance for Loan and Lease Losses [Roll Forward]
Loans and Leases Receivable, Allowance, beginning balance	$ 138,785	132,472
Allowance for Loan and Lease Losses, Write-offs		(32,262)
Allowance for Loan and Lease Loss, Recovery of Bad Debts		15,575
Allowance for Loan and Lease Losses Write-offs, Net		(16,687)
Provision for Loan and Lease Losses		23,000
Loans and Leases Receivable, Allowance, ending balance		138,785
Loans held for investment, net		$ 18,846,872

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ 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)(3)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Amount, after recoveries, of loans and leases that have been written-off.

+ References

No definition available.

+ Details

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

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

+ Details

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

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

+ Details

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

- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for 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 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=118939070&loc=d3e15032-111544

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

+ Details

Name:	us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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://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

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5074-111524

+ Details

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

- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

+ Details

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

- Details

Name:	srt_RestatementAxis=srt_ScenarioPreviouslyReportedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RestatementAxis=srt_RestatementAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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