XML 78 R67.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Fair Value of Financial Instruments - Carrying Values and Estimated Fair Values of Financial Instruments (Parenthetical) (Details) | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Percentage of coinsurance costs | 10.00% | 10.00%

X
- Definition Percentage of coinsurance covered costs. + References No definition available. + Details
Name: | pri_PercentageOfCoinsuranceCoveredCosts
Namespace Prefix: | pri_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |