2.2.0.25truefalse04190 - Disclosure - Credit Agreements (Details)truefalseIn Millions, unless otherwise specifiedfalse1falsefalseUSDfalsefalse12/31/2010 USD ($) $AS_OF_Dec31_2010http://www.sec.gov/CIK0000911421instant2010-12-31T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2falsefalseUSDtruefalse{pre_LineOfCreditFacilityByFacilityAxis} : Unsecured Syndicated Credit Facility A [Member] 1/1/2010 - 12/31/2010 FROM_Jan01_2010_TO_Dec31_2010_pre_LineOfCreditFacilityByFacilityAxis_UnsecuredSyndicatedCreditFacilityAMemberhttp://www.sec.gov/CIK0000911421duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseUnsecured Syndicated Credit Facility A [Member]pre_LineOfCreditFacilityByFacilityAxisxbrldihttp://xbrl.org/2006/xbrldipre_UnsecuredSyndicatedCreditFacilityAMemberpre_LineOfCreditFacilityByFacilityAxisexplicitMemberPureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170$3falsefalseUSDtruefalse{pre_LineOfCreditFacilityByFacilityAxis} : Unsecured Syndicated Credit Facility B [Member] 1/1/2010 - 12/31/2010 FROM_Jan01_2010_TO_Dec31_2010_pre_LineOfCreditFacilityByFacilityAxis_UnsecuredSyndicatedCreditFacilityBMemberhttp://www.sec.gov/CIK0000911421duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseUnsecured Syndicated Credit Facility B [Member]pre_LineOfCreditFacilityByFacilityAxisxbrldihttp://xbrl.org/2006/xbrldipre_UnsecuredSyndicatedCreditFacilityBMemberpre_LineOfCreditFacilityByFacilityAxisexplicitMemberPureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170$4falsefalseUSDtruefalse{pre_LineOfCreditFacilityByFacilityAxis} : Combined Credit Facility [Member] 1/1/2010 - 12/31/2010 FROM_Jan01_2010_TO_Dec31_2010_pre_LineOfCreditFacilityByFacilityAxis_CombinedCreditFacilityMemberhttp://www.sec.gov/CIK0000911421duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseCombined Credit Facility [Member]pre_LineOfCreditFacilityByFacilityAxisxbrldihttp://xbrl.org/2006/xbrldipre_CombinedCreditFacilityMemberpre_LineOfCreditFacilityByFacilityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170$5falsefalseUSDtruefalse{pre_LineOfCreditFacilityByFacilityAxis} : Committed Secured Letter Of Credit Facility A [Member] 1/1/2010 - 12/31/2010 FROM_Jan01_2010_TO_Dec31_2010_pre_LineOfCreditFacilityByFacilityAxis_CommittedSecuredLetterOfCreditFacilityAMemberhttp://www.sec.gov/CIK0000911421duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseCommitted Secured Letter Of Credit Facility A [Member]pre_LineOfCreditFacilityByFacilityAxisxbrldihttp://xbrl.org/2006/xbrldipre_CommittedSecuredLetterOfCreditFacilityAMemberpre_LineOfCreditFacilityByFacilityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170$6falsefalseUSDtruefalse{pre_LineOfCreditFacilityByFacilityAxis} : Committed Secured Letter Of Credit Facility B [Member] 1/1/2010 - 12/31/2010 FROM_Jan01_2010_TO_Dec31_2010_pre_LineOfCreditFacilityByFacilityAxis_CommittedSecuredLetterOfCreditFacilityBMemberhttp://www.sec.gov/CIK0000911421duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseCommitted Secured Letter Of Credit Facility B [Member]pre_LineOfCreditFacilityByFacilityAxisxbrldihttp://xbrl.org/2006/xbrldipre_CommittedSecuredLetterOfCreditFacilityBMemberpre_LineOfCreditFacilityByFacilityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170$7falsefalseUSDtruefalse{pre_LineOfCreditFacilityByFacilityAxis} : Committed Secured Letter Of Credit Facilities [Member] 12/31/2010 USD ($) $AS_OF_Dec31_2010_pre_LineOfCreditFacilityByFacilityAxis_CommittedSecuredLetterOfCreditFacilitiesMemberhttp://www.sec.gov/CIK0000911421instant2010-12-31T00:00:000001-01-01T00:00:00falsefalseCommitted Secured Letter Of Credit Facilities [Member]pre_LineOfCreditFacilityByFacilityAxisxbrldihttp://xbrl.org/2006/xbrldipre_CommittedSecuredLetterOfCreditFacilitiesMemberpre_LineOfCreditFacilityByFacilityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$8falsefalseUSDtruefalse{us-gaap_GuaranteeObligationsByNatureAxis} : Outstanding Unsecured Letter Of Credit [Member] 12/31/2010 USD ($) $AS_OF_Dec31_2010_us-gaap_GuaranteeObligationsByNatureAxis_OutstandingUnsecuredLetterOfCreditMemberhttp://www.sec.gov/CIK0000911421instant2010-12-31T00:00:000001-01-01T00:00:00falsefalseOutstanding Unsecured Letter Of Credit [Member]us-gaap_GuaranteeObligationsByNatureAxisxbrldihttp://xbrl.org/2006/xbrldipre_OutstandingUnsecuredLetterOfCreditMemberus-gaap_GuaranteeObligationsByNatureAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$9falsefalseUSDtruefalse{us-gaap_GuaranteeObligationsByNatureAxis} : Outstanding Secured Letter Of Credit [Member] 12/31/2010 USD ($) $AS_OF_Dec31_2010_us-gaap_GuaranteeObligationsByNatureAxis_OutstandingSecuredLetterOfCreditMemberhttp://www.sec.gov/CIK0000911421instant2010-12-31T00:00:000001-01-01T00:00:00falsefalseOutstanding Secured Letter Of Credit [Member]us-gaap_GuaranteeObligationsByNatureAxisxbrldihttp://xbrl.org/2006/xbrldipre_OutstandingSecuredLetterOfCreditMemberus-gaap_GuaranteeObligationsByNatureAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2true0pre_CreditAgreementsDetailsLineItemsprefalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseCredit Agreements Details [Line Items]3false0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacityus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsefalse13594000001359.4falsetruefalsefalsefalse2truefalsefalse660000000660.0falsetruefalsetruefalse3truefalsefalse750000000750.0falsetruefalsetruefalse4truefalsefalse250000000250.0falsetruefalsetruefalse5truefalsefalse150000000150.0falsetruefalsetruefalse6truefalsefalse200000000200.0falsetruefalsetruefalse7truefalsefalse350000000350.0falsetruefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryMaximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 4 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 falsefalseTotal amount of credit facilities available4false0us-gaap_LineOfCreditFacilityInitiationDateus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse007/16/20107/16/2010falsefalsefalsetruefalse4falsefalsefalse005/14/20105/14/2010falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseOtherus-types:dateStringItemTypenormalizedstringReflects when the credit facility first became available, which may be presented in a variety of ways (year, month and year, day, month and year, quarter).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 4 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 falsefalseInitiation date5false0us-gaap_LineOfCreditFacilityExpirationDateus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse009/30/20109/30/2010falsefalsefalsetruefalse3falsefalsefalse007/16/20137/16/2013falsefalsefalsetruefalse4falsefalsefalse005/4/20115/4/2011falsefalsefalsetruefalse5falsefalsefalse001/20/20121/20/2012falsefalsefalsetruefalse6falsefalsefalse0011/18/201111/18/2011falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseOtherus-types:dateStringItemTypenormalizedstringReflects when the credit facility terminates, which may be presented in a variety of ways (year, month and year, day, month and year, quarter).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 4 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 falsefalseMaturity date of facility6false0pre_LineOfCreditFacilityExtensionDateprefalsenadurationReflects when the credit facility terminates if an available extension is used.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse005/14/20125/14/2012falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseOtherus-types:dateStringItemTypenormalizedstringReflects when the credit facility terminates if an available extension is used.No authoritative reference available.falsefalseMaturity date of facility, extension7false0us-gaap_GuaranteeObligationsMaximumExposureus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8truefalsefalse459900000459.9falsefalsefalsetruefalse9truefalsefalse243200000243.2falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryMaximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Interpretation (FIN) -Number 45 -Paragraph 13 -Subparagraph b falsefalseLetters of credit issued as of balance sheet date8false0pre_LineOfCreditFacilityAccordionFeatureValueprefalsecreditinstantAdditional potential capacity under the line of credit facility, subject to lender agreement.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3truefalsefalse250000000250falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryAdditional potential capacity under the line of credit facility, subject to lender agreement.No authoritative reference available.falsefalseAccordion feature9false0pre_LineOfCreditFacilityMaximumBorrowingCapacityWithAccordionFeatureprefalsecreditinstantMaximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3truefalsefalse10000000001000falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryMaximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility, after application of the accordion feature.No authoritative reference available.falsefalseTotal borrowing capacity with accordion10false0pre_LineOfCreditFacilityUnsecuredLimitprefalsecreditinstantRepresents the amount of credit that is available on an unsecured basisfalsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4truefalsefalse100000000100falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryRepresents the amount of credit that is available on an unsecured basisNo authoritative reference available.falsefalseAmount of unsecured borrowing capacity11false0pre_LineOfCreditFacilityRevolvingCreditAmountprefalsecreditinstantAmount of line of credit facility available for use as a revolving line of credit.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3truefalsefalse375000000375falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryAmount of line of credit facility available for use as a revolving line of credit.No authoritative reference available.falsefalseRevolving credit amount12false0pre_LineOfCreditFacilityTermprefalsenadurationThe term of the line of credit facility, from issuance date to first maturity date.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse55falsefalsefalsetruefalse3truefalsefalse33falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseOtherxbrli:integerItemTypeintegerThe term of the line of credit facility, from issuance date to first maturity date.No authoritative reference available.falsefalseTerm of credit facility13false0us-gaap_LineOfCreditFacilityAmountOutstandingus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3truefalsefalse00falsetruefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryAmount borrowed under the credit facility as of the balance-sheet date.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 falsefalseBorrowings at balance sheet date912Credit Agreements (Details) (USD $)HundredThousandsUnKnownUnKnownUnKnowntruetrue