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Share-Based Transactions - Employee Share-Based Transactions, PSU Activity (Parenthetical) (Details) - Performance share units (PSUs) [Member] - ROAE Achieved Within Vesting Period [Member] - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares of common stock may be received by recipients	45,869,000	54,069,000	22,758,000
Minimum number of shares of common stock may be received by recipients	0	0

X

- Definition

Share based compensation arrangement by share based payment award minimum number of shares per employee.

+ References

No definition available.

+ Details

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Namespace Prefix:	pri_
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Balance Type:	na
Period Type:	duration

X

- 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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X

- Definition

The highest quantity of shares an employee can purchase under the plan per period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

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- Details

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- Details

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