Name:	pra_CreditLossesRecognizedInEarningsInWhichAPortionOfLossesAreRecognizedInComprehensiveIncomeLossCreditLossesOnDebtSecuritiesHeld
Namespace Prefix:	pra_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Impairment Loss, Debt Securities, No Impairment Previously Recognized

No definition available.

Name:	pra_ImpairmentLossDebtSecuritiesNoImpairmentPreviouslyRecognized
Namespace Prefix:	pra_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which a previous OTTI was recognized and the investor does not intend to sell the debt security and it is not more likely than not that the investor will be required to sell the debt security before recovery of its amortized cost basis.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 8B
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=SL6284393-111563

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

This item represents reductions in the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security because of the sale of impaired securities during the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 8B
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=SL6284393-111563

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

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.