Name:	pl_FutureScheduledCapitalContributions
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the term of the letter of credit of the entity.

No definition available.

Name:	pl_LetterOfCreditTerm
Namespace Prefix:	pl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the maximum amount up to which the borrowing capacity under the letter of credit arrangements will be increased.

No definition available.

Name:	pl_LettersOfCreditMaximumAmountUpToWhichBorrowingCapacityWillBeIncreased
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the maximum borrowing capacity under the letters of credit.

No definition available.

Name:	pl_LettersOfCreditMaximumBorrowingCapacity
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the number of installments in which future scheduled capital contributions are payable under support agreement obligation.

No definition available.

Name:	pl_NumberOfInstallmentsInWhichFutureScheduledCapitalContributionsIsPayable
Namespace Prefix:	pl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Repurchase Average Daily Balance At Average Interest Rate

No definition available.

Name:	pl_RepurchaseAverageDailyBalanceAtAverageInterestRate
Namespace Prefix:	pl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the average daily balance of reverse repurchase liability.

No definition available.

Name:	pl_ReverseRepurchaseAverageDailyBalance
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the average borrowing rate of average daily balance of the repurchase obligation.

No definition available.

Name:	pl_ReverseRepurchaseAverageDailyBalanceAtAverageInterestRate
Namespace Prefix:	pl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

This element represents proceeds from reverse repurchase liability for the balance sheet date.

No definition available.

Name:	pl_ReverseRepurchaseLiability
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the maximum outstanding balance of reverse repurchase liability.

No definition available.

Name:	pl_ReverseRepurchaseMaximumBalanceOutstanding
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Securities Lending, Percent Of Initial Collateral Required

No definition available.

Name:	pl_SecuritiesLendingPercentOfInitialCollateralRequired
Namespace Prefix:	pl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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.

No definition available.

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

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

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

The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

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

Fair value of the securities pledged as collateral against securities loaned.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226013-175313

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

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and financial assets transferred other than securities that qualify as secured borrowings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

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

Name:	us-gaap_LongtermDebtTypeAxis=pl_RepurchaseProgramBorrowingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_LegalEntityAxis=pl_GoldenGateIIIMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DebtInstrumentAxis=pl_ThirdAmendedandRestatedReimbursementAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DebtInstrumentAxis=pl_ReimbursementAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_LegalEntityAxis=pl_GoldenGateIVMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: