INVESTMENT OPERATIONS - Summary of Net Realized Investment Gains (Losses) for all Other Investments (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	5 Months Ended	6 Months Ended
Jan. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2016
Successor
Investment [Line Items]
Fixed maturities		$ 16,730	$ 3,339	$ 3,712	$ 22,451
Equity securities		202	21	21	36
Impairments on corporate securities		(964)	(5,734)	(5,734)	(3,581)
Modco trading portfolio		76,201	(108,741)	(141,901)	154,355
Other investments		(4,353)	3,044	775	(6,334)
Total realized gains (losses) - investments		$ 87,816	$ (108,071)	$ (143,127)	$ 166,927
Predecessor
Investment [Line Items]
Fixed maturities	$ 6,891
Equity securities	0
Impairments on corporate securities	(481)
Modco trading portfolio	73,062
Other investments	1,200
Total realized gains (losses) - investments	$ 80,672

No definition available.

Name:	invest_InvestmentLineItems
Namespace Prefix:	invest_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount by which the fair value of an investment in fixed maturity securities is less than the amortized cost basis or the carrying amount of that investment at the balance sheet date and the decline in the fair value is deemed to be other-than-temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

No definition available.

+ Details

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

- Definition

Represents the total realized gain (loss) included in earnings during the period as a result of investments other than derivative financial instruments, net of the amount recognized in earnings for other than temporary impairments (OTTI) of investments in debt and equity securities.

+ References

No definition available.

+ Details

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

- Definition

The difference between the carrying value and the sale price of debt securities, not separately or otherwise categorized as trading, available-for-sale, or held-to-maturity. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(h))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

+ Details

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

- Definition

The difference between the carrying value and the sale price of equity securities, not separately or otherwise categorized as trading or available-for-sale. This element includes investments in which the entity holds a small ownership stake (generally, less than 20% of the shares outstanding) and cannot exert significant influence.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(h))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

+ Details

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

- Definition

The difference between the book value and the sale price of other nonspecific investments. This element is used when other, more specific, elements are not appropriate. This element refers to the gain (loss) included in earnings.

+ References

+ Details

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

- Definition

Amount of gain (loss) realized from securities classified as trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(c))
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

+ Details

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

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_SuccessorMember
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: