SCHEDULE IV - Reinsurance (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reinsurance premiums
Gross amount	$ 73,567	$ 25,532	$ 8,390
Ceded to other companies	141,539	180,426	82,554
Assumed from other companies	4,715,726	4,931,365	4,193,989
Net amount	4,647,754	4,776,471	4,119,825
Percentage of amount assumed to net	101.00%	103.00%	102.00%
[LifeInsuranceInForceMember]
Life reinsurance in force
Gross amount	0
Ceded to other companies	1,673,196	1,726,050	1,636,933
Assumed from other companies	199,347,294	192,669,971	204,704,933
Net amount	197,674,098	190,943,921	203,068,000
Percentage of amount assumed to net	101.00%	101.00%	101.00%
[LifeInsuranceSegmentMember]
Reinsurance premiums
Gross amount	0
Ceded to other companies	3,470	5,118	4,608
Assumed from other companies	774,383	729,007	570,118
Net amount	770,913	723,889	565,510
Percentage of amount assumed to net	100.00%	101.00%	101.00%
[AccidentAndHealthInsuranceSegmentMember]
Reinsurance premiums
Gross amount	0
Ceded to other companies	0
Assumed from other companies	21,235	19,676	22,043
Net amount	21,235	19,676	22,043
Percentage of amount assumed to net	100.00%	100.00%	100.00%
[PropertyLiabilityAndCasualtyInsuranceSegmentMember]
Reinsurance premiums
Gross amount	73,567	25,532	8,390
Ceded to other companies	138,069	175,308	77,946
Assumed from other companies	3,920,108	4,182,682	3,601,828
Net amount	$ 3,855,606	$ 4,032,906	$ 3,532,272
Percentage of amount assumed to net	102.00%	104.00%	102.00%

Name:	pre_LifeReinsuranceInForceAbstract
Namespace Prefix:	pre_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the gross amount of death benefits (face amount of policies) assumed from other companies under reinsurance contracts in force as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	pre_LifeReinsuranceInForceAssumedFromOtherCompanies
Namespace Prefix:	pre_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the gross amount of death benefits (face amount of policies) ceded to other companies under reinsurance contracts in force as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	pre_LifeReinsuranceInForceCededToOtherCompanies
Namespace Prefix:	pre_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the gross amount of death benefits (face amount of policies) under reinsurance contracts in force as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	pre_LifeReinsuranceInForceGrossAmount
Namespace Prefix:	pre_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the net amount of death benefits (face amount of policies) under reinsurance contracts in force as of the balance sheet date. The net amount is calculated as the gross amount, less amounts ceded to other companies, plus amounts assumed from other companies.

+ References

No definition available.

+ Details

Name:	pre_LifeReinsuranceInForceNetAmount
Namespace Prefix:	pre_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The ratio of face amount of life reinsurance policies assumed to the net amount of of life reinsurance policies in force as of the balance sheet date..

+ References

No definition available.

+ Details

Name:	pre_LifeReinsuranceInForcePercentageOfAmountAssumedToNet
Namespace Prefix:	pre_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of premiums assumed from other companies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 235

-Section S99

-Paragraph 2

-Subparagraph (SX 210.12-17)

-URI http://asc.fasb.org/extlink&oid=6588446&loc=d3e574992-122915

+ Details

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

- Definition

Amount of premiums ceded to other companies.

+ References

+ Details

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

- Definition

Gross amount of premium revenue.

+ References

+ Details

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

- Definition

Net amount of gross premiums, less premiums ceded to other companies, plus premiums assumed from other companies; which represents the net amount of premium revenue on the income statement.

+ References

+ Details

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

- Details

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

- Definition

Percentage of amount of premiums assumed from other companies to net amount of premiums.

+ References

+ Details

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