OFFSETTING OF ASSETS AND LIABILITIES - Schedule of Derivative Instruments by Assets (Details) - Successor - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	$ 656,719	$ 352,016
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	656,719	352,016
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	114,968	42,382
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	299,819	105,842
Net Amount	241,932	203,792
Total derivatives, subject to a master netting arrangement or similar arrangement
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	586,545	254,840
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	586,545	254,840
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	114,968	42,382
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	299,819	105,842
Net Amount	171,758	106,616
Free-Standing derivatives
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	586,545	254,840
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	586,545	254,840
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	114,968	42,382
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	299,819	105,842
Net Amount	171,758	106,616
Total derivatives, not subject to a master netting arrangement or similar arrangement
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	70,174	97,176
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	70,174	97,176
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	0	0
Net Amount	70,174	97,176
Embedded derivative - Modco reinsurance treaties
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	2,787	1,215
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	2,787	1,215
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	0	0
Net Amount	2,787	1,215
Embedded derivative - GMWB
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	67,264	95,614
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	67,264	95,614
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	0	0
Net Amount	67,264	95,614
Other
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets	123	347
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	123	347
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	0	0
Net Amount	$ 123	$ 347

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and elected not to be offset.

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

- Definition

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226003-175313

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959

+ Details

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

- Definition

Fair value, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, offset against an obligation to return collateral.

+ References

+ Details

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

- Definition

Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be offset, deducted from derivative assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226016-175313

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(1)(i)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

+ Details

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

- Definition

Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement, deducted from derivative assets.

+ References

+ Details

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

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13433-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13495-108611

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313

+ Details

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

- Definition

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=d3e41678-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226016-175313

+ Details

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

- Definition

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

+ Details

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

- References

No definition available.

+ Details

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

- Details

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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=pl_DerivativesSubjecttoMasterNettingArrangementorSimilarArrangementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=pl_FreeStandingDerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=pl_DerivativesNotSubjecttoMasterNettingArrangementorSimilarArrangementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=pl_EmbeddedDerivativeModcoReinsuranceTreatiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=pl_EmbeddedDerivativeGMWBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=pl_OtherDerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: