Lessee, operating and finance leases, options to terminate leases term.

No definition available.

Name:	pri_LesseeOperatingAndFinanceLeasesOptionsToTerminateLeasesTerm
Namespace Prefix:	pri_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Lessee, operating and finance leases, remaining lease term.

+ References

No definition available.

+ Details

Name:	pri_LesseeOperatingAndFinanceLeasesRemainingLeaseTerm
Namespace Prefix:	pri_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Lessee, operating and finance leases, renewal term.

+ References

No definition available.

+ Details

Name:	pri_LesseeOperatingAndFinanceLeasesRenewalTerm
Namespace Prefix:	pri_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Present value of lessee's discounted obligation for lease payments from finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918701-209980

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

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

- Definition

Amount of lessee's right to use underlying asset under finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

Name:	us-gaap_FinanceLeaseRightOfUseAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Name:	us-gaap_LesseeLeaseDescriptionLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The increases or decreases in lease payments that result from changes occurring after the inception of the lease in the factors (other than the passage of time) on which lease payments are based, except that any escalation of minimum lease payments relating to increases in construction or acquisition cost of the leased property or for increases in some measure of cost or value during the construction or preconstruction period, are excluded from contingent rentals. Contingent rentals also may include amounts for which the triggering events have not yet occurred or the specified targets for which have not yet been achieved (such as sales based percentage rent), but which events are considered probable of occurring or which specified targets are considered probable of being achieved.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 40
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

+ Details

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

- Definition

This element represents the payments that the lessee is obligated to make or can be required to make in connection with a property under the terms of an agreement classified as an operating lease, excluding contingent rentals and a guarantee by the lessee of the lessor's debt and the lessee's obligation to pay (apart from the rental payments) executory costs such as insurance, maintenance, and taxes.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
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+ 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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- Details

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- Details

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Leases - Narratives (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Leases - Narratives (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Lessee Lease Description [Line Items]
Lease renewal term		10 years
Lease termination period		4 years
Finance lease liabilities		$ 797
Operating lease minimum rent expense	$ 2,000		$ 3,800
Operating lease contingent rent expense	$ 0		$ 0
Minimum [Member]
Lessee Lease Description [Line Items]
Remaining lease term		1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Remaining lease term		11 years
Other Assets
Lessee Lease Description [Line Items]
Finance right-of-use assets		$ 800
Other Liabilities
Lessee Lease Description [Line Items]
Finance lease liabilities		$ 800