FAIR VALUE OF FINANCIAL INSTRUMENTS (Details 4) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Mortgage loans on real estate	$ 5,728,237
Policy loans	1,706,402
Fixed maturities, held-to-maturity	579,329
Liabilities:
Stable value product account balances	1,914,093
Annuity account balances	10,754,799
Debt:
Subordinated debt securities	450,603
Non-recourse funding obligations	670,994
Golden Gate V
Debt:
Non-recourse funding obligations	550,079
Carrying Amounts \| Golden Gate V
Debt:
Non-recourse funding obligations	485,000
Fair Values \| Golden Gate V
Debt:
Non-recourse funding obligations	496,700
Predecessor
Assets:
Mortgage loans on real estate		$ 5,133,780
Policy loans		1,758,237
Fixed maturities, held-to-maturity		435,000
Liabilities:
Stable value product account balances		1,959,488
Annuity account balances		10,950,729
Debt:
Subordinated debt securities		540,593
Non-recourse funding obligations		582,404
Predecessor \| Carrying Amounts \| Golden Gate V
Debt:
Non-recourse funding obligations		435,000
Predecessor \| Fair Values \| Golden Gate V
Debt:
Non-recourse funding obligations		461,400
Level 3 \| Carrying Amounts
Assets:
Mortgage loans on real estate	5,728,237
Policy loans	1,706,402
Liabilities:
Stable value product account balances	1,914,093
Annuity account balances	10,754,799
Debt:
Bank borrowings	495,000
Non-recourse funding obligations	670,994
Level 3 \| Carrying Amounts \| Fixed maturities
Assets:
Fixed maturities, held-to-maturity	579,329
Level 3 \| Fair Values
Assets:
Mortgage loans on real estate	5,590,446
Policy loans	1,706,402
Liabilities:
Stable value product account balances	1,903,615
Annuity account balances	10,321,313
Debt:
Bank borrowings	495,000
Non-recourse funding obligations	615,816
Level 3 \| Fair Values \| Fixed maturities
Assets:
Fixed maturities, held-to-maturity	518,363
Level 3 \| Predecessor \| Carrying Amounts
Assets:
Mortgage loans on real estate		5,133,780
Policy loans		1,758,237
Liabilities:
Stable value product account balances		1,959,488
Annuity account balances		10,950,729
Debt:
Bank borrowings		450,000
Non-recourse funding obligations		582,404
Level 3 \| Predecessor \| Carrying Amounts \| Fixed maturities
Assets:
Fixed maturities, held-to-maturity		435,000
Level 3 \| Predecessor \| Fair Values
Assets:
Mortgage loans on real estate		5,524,059
Policy loans		1,758,237
Liabilities:
Stable value product account balances		1,973,624
Annuity account balances		10,491,775
Debt:
Bank borrowings		450,000
Non-recourse funding obligations		578,212
Level 3 \| Predecessor \| Fair Values \| Fixed maturities
Assets:
Fixed maturities, held-to-maturity		458,422
Level 2 \| Carrying Amounts
Debt:
Senior Notes	1,110,796
Subordinated debt securities	450,603
Level 2 \| Fair Values
Debt:
Senior Notes	1,035,041
Subordinated debt securities	$ 452,835
Level 2 \| Predecessor \| Carrying Amounts
Debt:
Senior Notes		850,000
Subordinated debt securities		540,593
Level 2 \| Predecessor \| Fair Values
Debt:
Senior Notes		1,100,380
Subordinated debt securities		$ 552,098

Represents the liability as of the balance sheet date of amounts held for annuity contracts.

No definition available.

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

- Definition

Non-recourse funding obligations issued by special purpose entities owned by the reporting entity. The funding obligations are direct financial obligations of the special purpose entity and are not guaranteed by the reporting entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the liability as of the balance sheet date of amounts related to stable value contracts.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.6)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Amount before allowance of loans made to policy and contract holders using their life insurance contracts' cash value or separate accounts as collateral. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums over and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

+ Details

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

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of loans from a bank with maturities initially due after one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

+ Details

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

- Definition

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.

+ References

+ Details

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

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

+ Details

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

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Article 5

-Subsection 19, 20, 22

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 10

-Section F

+ Details

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

- Details

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

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_PredecessorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_FixedMaturitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: