Debt Instrument, Outstanding Principal

No definition available.

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

- Definition

Extinguishment of Debt Par Value

+ References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility which can be granted upon request by the entity.

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

+ Details

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

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=98514028&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: 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

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- 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(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-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

+ Details

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

- Details

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Balance Type:
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- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SubordinatedDebtMember
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- Details

Name:	us-gaap_DebtInstrumentAxis=pl_SeniorNotes6.40PercentDue2018Member
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- Details

Name:	us-gaap_DebtInstrumentAxis=pl_SeniorNotes7.375PercentDue2019Member
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- Details

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- Details

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- Details

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- Details

Name:	us-gaap_CreditFacilityAxis=pl_AmendedLineOfCreditMember
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- Details

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DEBT AND OTHER OBLIGATIONS - Summary of Debt and Subordinated Debt Securities (Details) - USD ($)			6 Months Ended	12 Months Ended
	Feb. 03, 2015	Feb. 02, 2015	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Outstanding Principal			$ 988,865,000	$ 966,926,000
Carrying Amounts, Debt			1,163,531,000	1,163,285,000
Carrying Amounts, Subordinated debt securities			437,804,000	441,202,000
Capital lease obligation
Debt Instrument [Line Items]
Outstanding Principal			937,000	0
Carrying Amounts, Debt			937,000	0
Subordinated debt securities
Debt Instrument [Line Items]
Outstanding Principal			437,500,000	437,500,000
Carrying Amounts, Subordinated debt securities			437,804,000	441,202,000
6.40% Senior Notes (2007), due 2018
Debt Instrument [Line Items]
Outstanding Principal			150,000,000	150,000,000
Carrying Amounts, Debt			$ 153,608,000	$ 156,663,000
Stated interest rate (as a percent)			6.40%	6.40%
7.375% Senior Notes (2009), due 2019
Debt Instrument [Line Items]
Outstanding Principal			$ 400,000,000	$ 400,000,000
Carrying Amounts, Debt			$ 445,303,000	$ 454,688,000
Stated interest rate (as a percent)			7.375%	7.375%
8.45% Senior Notes (2009), due 2039
Debt Instrument [Line Items]
Outstanding Principal			$ 232,928,000	$ 246,926,000
Carrying Amounts, Debt			$ 358,683,000	$ 381,934,000
Stated interest rate (as a percent)			8.45%	8.45%
Debt repurchased and subsequently extinguished			$ 21,600,000	$ 82,700,000
Par value of extinguished debt			14,000,000	53,100,000
Pre-tax gain (loss) on extinguishment of debt			$ 2,000,000	$ 9,800,000
6.25% Subordinated Debentures (2012), due 2042, callable 2017
Debt Instrument [Line Items]
Stated interest rate (as a percent)			6.25%	6.25%
6.25% Subordinated Debentures (2012), due 2042, callable 2017 \| Subordinated debt securities
Debt Instrument [Line Items]
Outstanding Principal			$ 287,500,000	$ 287,500,000
Carrying Amounts, Subordinated debt securities			$ 287,500,000	$ 290,002,000
6.00% Subordinated Debentures (2012), due 2042, callable 2017
Debt Instrument [Line Items]
Stated interest rate (as a percent)			6.00%	6.00%
6.00% Subordinated Debentures (2012), due 2042, callable 2017 \| Subordinated debt securities
Debt Instrument [Line Items]
Outstanding Principal			$ 150,000,000	$ 150,000,000
Carrying Amounts, Subordinated debt securities			150,304,000	151,200,000
Revolving Line of Credit
Debt Instrument [Line Items]
Outstanding Principal			205,000,000	170,000,000
Carrying Amounts, Debt			205,000,000	$ 170,000,000
Credit Facility
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity			1,000,000,000.0
Line of credit, maximum borrowing capacity to be granted upon entity's request			1,250,000,000.00
Facility fee percentage	0.125%	0.15%
Line of credit, amount outstanding			$ 205,000,000
Credit Facility \| Federal Funds Rate
Debt Instrument [Line Items]
Interest rate added to the base rate (as a percent)			0.50%
Credit Facility \| One-Month LIBOR
Debt Instrument [Line Items]
Interest rate added to the base rate (as a percent)			1.00%
Credit Facility \| LIBOR
Debt Instrument [Line Items]
Interest rate added to the base rate (as a percent)			1.00%