Debt Instrument, Repurchased Face Amount, Accrued and Unpaid Interest

No definition available.

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Namespace Prefix:	plmr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Instrument, Repurchased Face Amount, Redemption Price

+ References

No definition available.

+ Details

Name:	plmr_DebtInstrumentRepurchasedFaceAmountRedemptionPrice
Namespace Prefix:	plmr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Total redemption charge recognized during the period.

+ References

No definition available.

+ Details

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Namespace Prefix:	plmr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

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

- References

No definition available.

+ Details

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

- Definition

The excess of the (1) fair value of consideration transferred to the holders of a security in excess of (2) the carrying amount of the security reported on the registrant's balance sheet, which will be deducted from net earnings to derive net earnings available to common shareholders. This amount is generally an adjustment considered in the computation of earnings per share.

+ References

No definition available.

+ Details

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

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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

- Details

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- Details

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Data Type:	na
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- Details

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- Details

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- Details

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Long-term debt - Floating Rate Notes (Details) - Senior Notes - 2018 Floating Rate Notes - USD ($) $ in Millions		1 Months Ended	9 Months Ended
	May 23, 2019	Sep. 30, 2018	Sep. 30, 2019
Long-term debt
Debt instrument, redemption price, percentage (as a percent)	102.00%	100.00%
Redemption price	$ 20.4
Accrued interest and unpaid interest	0.3
Redemption charge	1.3
Redemption Premium	0.4		$ 0.4
Write-off of unamortized debt issuance costs	0.9
Interest Expense.
Long-term debt
Redemption Premium	0.4
Other Underwriting Expense
Long-term debt
Write-off of unamortized debt issuance costs	$ 0.9
Three-month Treasury Rate
Long-term debt
Interest rate spread (as a percent)		6.50%