2.2.0.25truefalse04180 - Disclosure - Off-Balance Sheet Arrangements (Details)truefalseShare data in Millions, unless otherwise specifiedfalse1falsefalsetruefalse{us-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxis} : Forward Contracts Member 10/1/2005 - 10/31/2005 FROM_Oct01_2005_TO_Oct31_2005_us-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxis_ForwardContractsMemberhttp://www.sec.gov/CIK0000911421duration2005-10-01T00:00:002005-10-31T00:00:00falsefalseForward Contracts Memberus-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_ForwardContractsMemberus-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxisexplicitMemberSharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli02falsefalseUSDtruefalse{us-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxis} : Forward Contracts Member 1/1/2010 - 12/31/2010 FROM_Jan01_2010_TO_Dec31_2010_us-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxis_ForwardContractsMemberhttp://www.sec.gov/CIK0000911421duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseForward Contracts Memberus-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_ForwardContractsMemberus-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxisexplicitMemberSharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170$3falsefalseUSDtruefalse{us-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxis} : Forward Contracts Member 1/1/2008 - 12/31/2008 USD ($) $FROM_Jan01_2008_TO_Dec31_2008_us-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxis_ForwardContractsMemberhttp://www.sec.gov/CIK0000911421duration2008-01-01T00:00:002008-12-31T00:00:00falsefalseForward Contracts Memberus-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_ForwardContractsMemberus-gaap_FairValueOffBalanceSheetRisksByFinancialInstrumentAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2true0us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItemsus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringLine 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.falsefalseFair Value Off Balance Sheet Risks Disclosure Information [Line Items]3false0pre_NumberOfSharesForwardAgreementprefalsenadurationThe total number of the Company's common shares under the forward sale agreement entered into with affiliate of Citigroup...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse67000006.7falsefalsefalsefalsefalse2truefalsefalse34000003.4falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseSharesxbrli:sharesItemTypesharesThe total number of the Company's common shares under the forward sale agreement entered into with affiliate of Citigroup Capital Markets Inc.No authoritative reference available.falsefalseTotal number of shares of forward sale agreement4false0pre_OriginalForwardAgreementSettlementSharesprefalsenadurationThe number of common shares delivered to the counterparty of the forward sale agreement, pursuant to terms of the original...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3truefalsefalse34000003.4falsefalsefalsefalsefalseSharesxbrli:sharesItemTypesharesThe number of common shares delivered to the counterparty of the forward sale agreement, pursuant to terms of the original agreement.No authoritative reference available.falsefalseOriginal forward agreement settlement5false0pre_OriginalForwardAgreementSettlementProceedsprefalsecreditinstantThe total proceeds received from the counterparty on settlement of half of the original forward sale agreement.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3truefalsefalse211600000211600000falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe total proceeds received from the counterparty on settlement of half of the original forward sale agreement.No authoritative reference available.falsefalseProceeds on original forward agreement settlement6false0pre_ExtendedForwardAgreementSettlementSharesprefalsenadurationThe number of the Company's common shares under the extended forward sale agreement that matured on April 28, 2010.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseSharesxbrli:sharesItemTypesharesThe number of the Company's common shares under the extended forward sale agreement that matured on April 28, 2010.No authoritative reference available.falsefalseExtended forward agreement settlement7false0pre_FaceValueOfExtendedForwardSaleAgreementprefalsecreditinstantThe face amount of the extended forward sale agreement, which is not recognized in the financial statements (off-balance...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse200000000200000000falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe face amount of the extended forward sale agreement, which is not recognized in the financial statements (off-balance sheet) because it fails to meet some other criterion for recognition.No authoritative reference available.falsefalseFace value of extended forward agreement settlement8false0pre_ExtendedForwardAgreementSettlementValuationPeriodprefalsenadurationThe number of days of the valuation period under which the Company could deliver the remaining number of Tranche 2 shares.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse4040falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:integerItemTypeintegerThe number of days of the valuation period under which the Company could deliver the remaining number of Tranche 2 shares.No authoritative reference available.falsefalseValuation period9false0pre_ExtendedForwardAgreementSettlementPricePerShareLowprefalsenainstantThe minimum price per common share during the valuation period, in accordance with the extended forward sale agreement.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse59.0559.05falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:decimalItemTypedecimalThe minimum price per common share during the valuation period, in accordance with the extended forward sale agreement.No authoritative reference available.falsefalseValuation period - value low10false0pre_ExtendedForwardAgreementSettlementPricePerShareHighprefalsenainstantThe maximum price per common share during the valuation period, in accordance with the extended forward sale agreement.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse84.1584.15falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:decimalItemTypedecimalThe maximum price per common share during the valuation period, in accordance with the extended forward sale agreement.No authoritative reference available.falsefalseValuation period - value high11false0pre_AdjustmentsToAdditionalPaidInCapitalOtherprefalsedebitdurationRepresents increases or decreases in additional paid in capital not separately disclosed.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3truefalsefalse81000008100000falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryRepresents increases or decreases in additional paid in capital not separately disclosed.No authoritative reference available.falsefalseContract fees recorded against APIC310Off-Balance Sheet Arrangements (Details) (Forward Contracts Member, USD $)NoRoundingHundredThousandsUnKnownUnKnowntruetrue