Name:	pl_FinancingReceivableAmountOfNonperformingForeclosedAndRestructuredLoans
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the minimum number of days over which the entity's policy is to cease carrying accrued interest on loans.

No definition available.

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

Represents the minimum number of days over which the entity's policy is to initiate foreclosure proceedings.

No definition available.

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

The maximum number of days of accrued interest that can be carried on an impaired loan.

No definition available.

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

Represents the average size of mortgage loans on real estate held in the portfolio on the balance sheet date.

No definition available.

Name:	pl_MortgageLoansOnRealEstateAverageSizeOfLoans
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the percentage of the mortgage loan portfolio represented by an single tenant.

No definition available.

Name:	pl_MortgageLoansOnRealEstateExposureToSingleTenant
Namespace Prefix:	pl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the amount of mortgage loans on real estate due to the entity in the next fiscal year following the latest fiscal year ended, if the loans are called at their next call dates.

No definition available.

Name:	pl_MortgageLoansOnRealEstateIfCalledDueInNextFiscalYear
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the amount of mortgage loans on real estate due to the entity in the seventh fiscal year through the eleventh fiscal year following the latest fiscal year, if the loans are called at their next call dates.

No definition available.

Name:	pl_MortgageLoansOnRealEstateIfCalledDueYearSevenToEleven
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the amount of mortgage loans on real estate due to the entity in the second fiscal year through the sixth fiscal year following the latest fiscal year, if the loans are called at their next call dates.

No definition available.

Name:	pl_MortgageLoansOnRealEstateIfCalledDueYearTwoThroughSix
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the amount of the largest mortgage loan on real estate held in the portfolio as of the balance sheet date.

No definition available.

Name:	pl_MortgageLoansOnRealEstateLargestLoanAmount
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the loan-to-value ratio permitted on commercial mortgage loans in exchange for a participating interest in the cash flows from the underlying property.

No definition available.

Name:	pl_MortgageLoansOnRealEstateLoanToValueRatioParticipatingInterest
Namespace Prefix:	pl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the average size of new mortgage loans on real estate during the reporting period.

No definition available.

Name:	pl_MortgageLoansOnRealEstateNewMortgageLoansAverageSizeOfLoans
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the amount of mortgage loans as of the balance sheet date which has a feature providing the entity a participating interest in the cash flows from the underlying real estate.

No definition available.

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

Represents the amount of income earned during the period on mortgage loans, which have a feature providing the entity a participating interest in the cash flows from the underlying real estate.

No definition available.

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

Represents the period within which the call option or interest rate reset option on the mortgage loan on real estate can be exercised.

No definition available.

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

Represents mortgage loans on real estate as a percentage of the total portfolio.

No definition available.

Name:	pl_PercentageOfMortgageLoansOnRealEstate
Namespace Prefix:	pl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Interest rate of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Paragraph Column B
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column B))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Name:	srt_MortgageLoansOnRealEstateInterestRate
Namespace Prefix:	srt_
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:	srt_MortgageLoansOnRealEstateLineItems
Namespace Prefix:	srt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

A valuation allowance for financing receivables that are expected to be uncollectible.

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)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(c))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

Amount of increase in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, from new investment.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Footnote 6))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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

Name:	srt_StatementGeographicalAxis=stpr_FL
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Name:	srt_StatementGeographicalAxis=stpr_AL
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Name:	srt_StatementGeographicalAxis=stpr_TX
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Name:	srt_StatementGeographicalAxis=stpr_GA
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Name:	srt_StatementGeographicalAxis=stpr_CA
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Name:	srt_StatementGeographicalAxis=stpr_MI
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Name:	srt_StatementGeographicalAxis=stpr_TN
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Name:	srt_StatementGeographicalAxis=stpr_UT
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Name:	srt_StatementGeographicalAxis=stpr_OH
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Name:	srt_StatementGeographicalAxis=stpr_NC
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_StatementGeographicalAxis=pl_IdentifiedStatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_RetailSiteMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_OfficeBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_ApartmentBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_WarehouseMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_MultifamilyMember
Namespace Prefix:
Data Type:	na
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_OtherPropertyMember
Namespace Prefix:
Data Type:	na
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Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
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