pfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationpfg:OperatingExpensesIncludingDeferredAcquisitionCostsCapitalizationAndAmortizationus-gaap:PropertyPlantAndEquipmentNetus-gaap:PropertyPlantAndEquipmentNetus-gaap:OtherLiabilitiesus-gaap:OtherLiabilities0001126328--12-312020FYfalsePFG7760000010000000.0605us-gaap:PropertyPlantAndEquipmentNetus-gaap:PropertyPlantAndEquipmentNetus-gaap:OtherLiabilitiesus-gaap:OtherLiabilitiesus-gaap:ValuationTechniqueDiscountedCashFlowMembergaap:ValuationTechniqueDiscountedCashFlowMembergaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:ValuationTechniqueDiscountedCashFlowMembergaap:ValuationTechniqueDiscountedCashFlowMembergaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember0P3YP3YP3YP1Y0001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:CorporateDebtSecuritiesMember2020-12-310001126328pfg:TradingSecuritiesMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2020-12-310001126328pfg:TradingSecuritiesMemberus-gaap:OtherDebtSecuritiesMember2020-12-310001126328pfg:TradingSecuritiesMemberus-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310001126328pfg:TradingSecuritiesMemberus-gaap:CollateralizedDebtObligationsMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:OtherDebtSecuritiesMember2019-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:CorporateDebtSecuritiesMember2019-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:CollateralizedDebtObligationsMember2019-12-310001126328pfg:TradingSecuritiesMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2019-12-310001126328pfg:TradingSecuritiesMemberus-gaap:OtherDebtSecuritiesMember2019-12-310001126328pfg:TradingSecuritiesMemberus-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310001126328pfg:TradingSecuritiesMemberus-gaap:CollateralizedDebtObligationsMember2019-12-310001126328us-gaap:EquitySecuritiesMember2019-12-310001126328us-gaap:TreasuryStockMember2020-01-012020-12-310001126328us-gaap:TreasuryStockMember2019-01-012019-12-310001126328us-gaap:TreasuryStockMember2018-01-012018-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:USTreasuryAndGovernmentMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:RedeemablePreferredStockMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:PublicUtilityBondsMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:OtherDebtSecuritiesMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:DebtSecuritiesMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:CollateralizedDebtObligationsMember2020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:AllOtherCorporateBondsMember2020-12-310001126328pfg:TradingSecuritiesMemberus-gaap:DebtSecuritiesMember2020-12-310001126328us-gaap:RealEstateInvestmentMember2020-12-310001126328us-gaap:RealEstateAcquiredInSatisfactionOfDebtMember2020-12-310001126328us-gaap:PublicUtilityEquitiesMember2020-12-310001126328us-gaap:PolicyLoansMember2020-12-310001126328us-gaap:OtherLongTermInvestmentsMember2020-12-310001126328us-gaap:NonredeemablePreferredStockMember2020-12-310001126328us-gaap:IndustrialMiscellaneousAndAllOthersMember2020-12-310001126328us-gaap:EquitySecuritiesMember2020-12-310001126328us-gaap:BanksTrustAndInsuranceEquitiesMember2020-12-310001126328pfg:OtherCorporateEquitiesMember2020-12-310001126328pfg:MortgageLoansMember2020-12-310001126328us-gaap:TreasuryStockMember2020-12-310001126328us-gaap:RetainedEarningsMember2020-12-310001126328us-gaap:NoncontrollingInterestMember2020-12-310001126328us-gaap:AdditionalPaidInCapitalMember2020-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201613Memberus-gaap:RetainedEarningsMember2019-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201613Member2019-12-310001126328us-gaap:TreasuryStockMember2019-12-310001126328us-gaap:RetainedEarningsMember2019-12-310001126328us-gaap:NoncontrollingInterestMember2019-12-310001126328us-gaap:AdditionalPaidInCapitalMember2019-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201602Memberus-gaap:RetainedEarningsMember2018-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201602Member2018-12-310001126328us-gaap:TreasuryStockMember2018-12-310001126328us-gaap:RetainedEarningsMember2018-12-310001126328us-gaap:NoncontrollingInterestMember2018-12-310001126328us-gaap:AdditionalPaidInCapitalMember2018-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201802Memberus-gaap:RetainedEarningsMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201601Memberus-gaap:RetainedEarningsMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201409Memberus-gaap:RetainedEarningsMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201409Memberus-gaap:NoncontrollingInterestMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberpfg:AccountingStandardsUpdateAsu201616Memberus-gaap:RetainedEarningsMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201409Member2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberpfg:AccountingStandardsUpdateAsu201616Member2017-12-310001126328us-gaap:TreasuryStockMember2017-12-310001126328us-gaap:RetainedEarningsMember2017-12-310001126328us-gaap:NoncontrollingInterestMember2017-12-310001126328us-gaap:AdditionalPaidInCapitalMember2017-12-310001126328us-gaap:AccumulatedTranslationAdjustmentMember2020-12-310001126328us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-12-310001126328us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2020-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201613Memberus-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201613Memberpfg:AccumulatedNoncreditOtherThanTemporaryImpairmentMember2019-12-310001126328us-gaap:AccumulatedTranslationAdjustmentMember2019-12-310001126328us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310001126328us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-12-310001126328us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2019-12-310001126328pfg:AccumulatedNoncreditOtherThanTemporaryImpairmentMember2019-12-310001126328us-gaap:AccumulatedTranslationAdjustmentMember2018-12-310001126328us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310001126328us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2018-12-310001126328us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2018-12-310001126328pfg:AccumulatedNoncreditOtherThanTemporaryImpairmentMember2018-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201802Memberus-gaap:AccumulatedTranslationAdjustmentMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201802Memberus-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201802Memberus-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201802Memberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201802Memberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201802Memberpfg:AccumulatedNoncreditOtherThanTemporaryImpairmentMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201601Memberus-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201601Memberus-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201409Memberus-gaap:AccumulatedTranslationAdjustmentMember2017-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201409Memberus-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310001126328us-gaap:AccumulatedTranslationAdjustmentMember2017-12-310001126328us-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310001126328us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2017-12-310001126328us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2017-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2017-12-310001126328pfg:AccumulatedNoncreditOtherThanTemporaryImpairmentMember2017-12-310001126328pfg:SubsidiariesPrincipalLifeInsuranceCompanyMember2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMember2019-01-012019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMember2018-01-012018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Member2020-12-310001126328pfg:GroupLifeMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Member2020-12-310001126328pfg:GroupLifeMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Member2020-12-310001126328pfg:DentalVisionShortTermDisabilityCriticalIllnessAccidentMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Member2020-12-310001126328pfg:DentalVisionShortTermDisabilityCriticalIllnessAccidentMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Member2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Member2019-12-310001126328pfg:GroupLifeMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Member2019-12-310001126328pfg:DentalVisionShortTermDisabilityCriticalIllnessAccidentMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Member2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2018-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2017-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2017-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2017-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2016-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2016-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2016-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2015-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2015-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2015-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2014-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2014-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2014-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2013-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2013-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2012-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2011-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMember2020-01-012020-12-310001126328pfg:GroupLifeMember2020-01-012020-12-310001126328pfg:DentalVisionShortTermDisabilityCriticalIllnessAccidentMember2020-01-012020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMembersrt:MinimumMember2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMembersrt:MaximumMember2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMembersrt:MinimumMember2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMembersrt:MaximumMember2019-12-310001126328pfg:DentalVisionShortTermDisabilityCriticalIllnessAccidentMember2020-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMember2019-12-310001126328pfg:GroupLifeMember2019-12-310001126328pfg:DentalVisionShortTermDisabilityCriticalIllnessAccidentMember2019-12-310001126328us-gaap:CommonStockMember2020-12-310001126328us-gaap:CommonStockMember2019-12-310001126328us-gaap:CommonStockMember2018-12-310001126328us-gaap:CommonStockMember2017-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceTotalRangeMember2020-01-012020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange5Member2020-01-012020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange4Member2020-01-012020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange3Member2020-01-012020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange2Member2020-01-012020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange1Member2020-01-012020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceTotalRangeMember2020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange5Member2020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange4Member2020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange3Member2020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange2Member2020-12-310001126328us-gaap:EmployeeStockOptionMemberpfg:ExercisePriceRange1Member2020-12-310001126328us-gaap:EmployeeStockOptionMember2019-12-310001126328pfg:StockBasedCompensationPlans2014StockIncentivePlanAmendedAndRestated2010StockIncentivePlanStockIncentivePlanMember2019-01-012019-12-310001126328pfg:StockBasedCompensationPlans2014StockIncentivePlanAmendedAndRestated2010StockIncentivePlanStockIncentivePlanMember2018-01-012018-12-310001126328pfg:StockIncentivePlansMember2020-12-310001126328us-gaap:RestrictedStockUnitsRSUMember2019-12-310001126328us-gaap:PerformanceSharesMember2019-12-310001126328pfg:StockBasedCompensationPlansStockIncentivePlanDirectorsStockPlanMember2006-01-012020-12-310001126328us-gaap:RestrictedStockUnitsRSUMemberpfg:StockBasedCompensationPlans2020DirectorsStockPlan2014DirectorsStockPlan2005DirectorsStockPlanMember2020-01-012020-12-310001126328us-gaap:RestrictedStockUnitsRSUMemberpfg:StockBasedCompensationPlans2014StockIncentivePlanAmendedAndRestated2010StockIncentivePlanStockIncentivePlanMember2020-01-012020-12-310001126328pfg:StockBasedCompensationPlans2014StockIncentivePlanAmendedAndRestated2010StockIncentivePlanStockIncentivePlanMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:DepositAccountMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsSpreadMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentSpecialtyBenefitsInsuranceMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CommissionIncomeMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CommissionIncomeMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsSpreadMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:ManagementServiceMemberpfg:SegmentPrincipalInternationalMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:ManagementServiceMemberpfg:SegmentPrincipalGlobalInvestorsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentPrincipalInternationalMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentPrincipalGlobalInvestorsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentCorporateMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMembersrt:LatinAmericaMemberpfg:SegmentPrincipalInternationalMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMembersrt:AsiaMemberpfg:SegmentPrincipalInternationalMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentUSInsuranceSolutionsEliminationsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentGeographicalAreaEliminationsMemberpfg:SegmentPrincipalInternationalMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:ProductsAndServicesEliminationsMemberpfg:SegmentCorporateMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CorporateAndRegionalMemberpfg:SegmentPrincipalInternationalMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CommissionIncomeMemberpfg:SegmentCorporateMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:DepositAccountMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsSpreadMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentSpecialtyBenefitsInsuranceMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CommissionIncomeMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:ManagementServiceMemberpfg:SegmentPrincipalInternationalMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:ManagementServiceMemberpfg:SegmentPrincipalGlobalInvestorsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentPrincipalInternationalMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentPrincipalGlobalInvestorsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentCorporateMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMembersrt:LatinAmericaMemberpfg:SegmentPrincipalInternationalMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMembersrt:AsiaMemberpfg:SegmentPrincipalInternationalMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentUSInsuranceSolutionsEliminationsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentGeographicalAreaEliminationsMemberpfg:SegmentPrincipalInternationalMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:ProductsAndServicesEliminationsMemberpfg:SegmentCorporateMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CorporateAndRegionalMemberpfg:SegmentPrincipalInternationalMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CommissionIncomeMemberpfg:SegmentCorporateMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:DepositAccountMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsSpreadMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentSpecialtyBenefitsInsuranceMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:AdministrativeServiceMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CommissionIncomeMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:ManagementServiceMemberpfg:SegmentPrincipalInternationalMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:ManagementServiceMemberpfg:SegmentPrincipalGlobalInvestorsMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentPrincipalInternationalMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentPrincipalGlobalInvestorsMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentCorporateMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMembersrt:LatinAmericaMemberpfg:SegmentPrincipalInternationalMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMembersrt:AsiaMemberpfg:SegmentPrincipalInternationalMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentUSInsuranceSolutionsEliminationsMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentGeographicalAreaEliminationsMemberpfg:SegmentPrincipalInternationalMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:ProductsAndServicesEliminationsMemberpfg:SegmentCorporateMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CorporateAndRegionalMemberpfg:SegmentPrincipalInternationalMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:CommissionIncomeMemberpfg:SegmentCorporateMember2018-01-012018-12-310001126328pfg:NotesPayable6.05PercentDue2036Memberus-gaap:SeniorNotesMember2016-10-012016-12-310001126328pfg:NotesPayable7.875PercentDue2014Memberus-gaap:SeniorNotesMember2012-09-052012-09-050001126328pfg:NotesPayable8.2PercentDue2009Memberus-gaap:SeniorNotesMember2009-08-152009-08-150001126328pfg:OperatingExpensesMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2020-01-012020-12-310001126328pfg:NetRealizedCapitalGainsLossesMemberus-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember2020-01-012020-12-310001126328pfg:NetRealizedCapitalGainsLossesMemberus-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2020-01-012020-12-310001126328pfg:NetIncomeLossAttributableToNoncontrollingInterestMemberus-gaap:AccumulatedForeignCurrencyAdjustmentAttributableToNoncontrollingInterestMember2020-01-012020-12-310001126328pfg:OperatingExpensesMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2019-01-012019-12-310001126328pfg:NetRealizedCapitalGainsLossesMemberus-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember2019-01-012019-12-310001126328pfg:NetRealizedCapitalGainsLossesMemberus-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2019-01-012019-12-310001126328pfg:NetIncomeLossAttributableToNoncontrollingInterestMemberus-gaap:AccumulatedForeignCurrencyAdjustmentAttributableToNoncontrollingInterestMember2019-01-012019-12-310001126328pfg:OperatingExpensesMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2018-01-012018-12-310001126328pfg:NetRealizedCapitalGainsLossesMemberus-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember2018-01-012018-12-310001126328us-gaap:FinanceLeasesPortfolioSegmentMember2020-01-022020-12-310001126328pfg:ReinsuranceRecoverablesMember2020-01-022020-12-310001126328pfg:SubsegmentIndividualLifeInsuranceMember2020-01-012020-12-310001126328pfg:SubsegmentIndividualLifeInsuranceMember2019-01-012019-12-310001126328pfg:SubsegmentIndividualLifeInsuranceMember2018-01-012018-12-310001126328pfg:AccumulatedNoncreditOtherThanTemporaryImpairmentMember2019-01-012019-12-310001126328pfg:AccumulatedNoncreditOtherThanTemporaryImpairmentMember2018-01-012018-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:NetInvestmentHedgingMember2020-01-012020-12-310001126328us-gaap:NetInvestmentHedgingMember2020-01-012020-12-310001126328pfg:FixedMaturitiesSecuritiesAvailableForSaleMemberus-gaap:InterestRateContractMember2020-01-012020-12-310001126328pfg:FixedMaturitiesSecuritiesAvailableForSaleMemberus-gaap:ForeignExchangeContractMember2020-01-012020-12-310001126328pfg:FixedMaturitiesSecuritiesAvailableForSaleMemberus-gaap:InterestRateContractMember2019-01-012019-12-310001126328pfg:FixedMaturitiesSecuritiesAvailableForSaleMemberus-gaap:ForeignExchangeContractMember2019-01-012019-12-310001126328pfg:InvestmentContractMemberus-gaap:ForeignExchangeContractMember2018-01-012018-12-310001126328pfg:FixedMaturitiesSecuritiesAvailableForSaleMemberus-gaap:InterestRateContractMember2018-01-012018-12-310001126328pfg:FixedMaturitiesSecuritiesAvailableForSaleMemberus-gaap:ForeignExchangeContractMember2018-01-012018-12-310001126328us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2018-01-012018-12-310001126328us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2020-01-012020-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2020-01-012020-12-310001126328us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2019-01-012019-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2019-01-012019-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember2018-01-012018-12-310001126328us-gaap:AccumulatedTranslationAdjustmentMember2020-01-012020-12-310001126328us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2020-01-012020-12-310001126328us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-01-012020-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2020-01-012020-12-310001126328us-gaap:AccumulatedTranslationAdjustmentMember2019-01-012019-12-310001126328us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-01-012019-12-310001126328us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-01-012019-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2019-01-012019-12-310001126328us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2018-01-012018-12-310001126328us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-01-012018-12-310001126328us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2018-01-012018-12-310001126328pfg:StandardPoorsBPlusAndBelowRatingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:StandardPoorsBPlusAndBelowRatingMemberpfg:CommercialBrickAndMortarMortgageMember2019-12-310001126328pfg:StandardPoorsBBPlusThruBBMinusRatingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:StandardPoorsBBPlusThruBBMinusRatingMemberpfg:CommercialBrickAndMortarMortgageMember2019-12-310001126328pfg:StandardPoorsBBBPlusThruBBBMinusRatingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:StandardPoorsBBBPlusThruBBBMinusRatingMemberpfg:CommercialCreditTenantMortgageMember2019-12-310001126328pfg:StandardPoorsBBBPlusThruBBBMinusRatingMemberpfg:CommercialBrickAndMortarMortgageMember2019-12-310001126328pfg:StandardPoorsAMinusAndAboveRatingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:StandardPoorsAMinusAndAboveRatingMemberpfg:CommercialCreditTenantMortgageMember2019-12-310001126328pfg:StandardPoorsAMinusAndAboveRatingMemberpfg:CommercialBrickAndMortarMortgageMember2019-12-310001126328pfg:PerformingMemberus-gaap:ResidentialMortgageMember2019-12-310001126328pfg:PerformingMemberus-gaap:HomeEquityMember2019-12-310001126328pfg:PerformingMemberus-gaap:FirstMortgageMember2019-12-310001126328pfg:NonperformingMemberus-gaap:ResidentialMortgageMember2019-12-310001126328pfg:NonperformingMemberus-gaap:HomeEquityMember2019-12-310001126328pfg:NonperformingMemberus-gaap:FirstMortgageMember2019-12-310001126328us-gaap:AccumulatedTranslationAdjustmentMember2018-01-012018-12-310001126328pfg:LawsuitAllegingBreachOfFiduciaryDutyInConnectionWithPrincipalFixedIncomeOptionMember2020-12-310001126328pfg:PrincipalInternationalChileMemberpfg:UnsecuredLineOfCreditMember2020-12-310001126328pfg:PrincipalFinancialServicesIncAndPrincipalLifeInsuranceCompanyAndPrincipalFinancialServicesVLTDAndPrincipalFinancialGroupCoborrowersMemberpfg:CreditFacilityMaturingNovember2023Member2020-12-310001126328pfg:PrincipalFinancialServicesIncAndPrincipalLifeInsuranceCompanyAndPrincipalFinancialGroupCoborrowersMemberpfg:CreditFacilityMaturingNovember2023Member2020-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:UnsecuredLineOfCreditMaturingSeptember2020Member2019-12-310001126328pfg:PrincipalInternationalChileMemberpfg:UnsecuredLineOfCreditMember2019-12-310001126328pfg:PrincipalFinancialServicesIncAndPrincipalLifeInsuranceCompanyAndPrincipalFinancialServicesVLTDAndPrincipalFinancialGroupCoborrowersMemberpfg:CreditFacilityMaturingNovember2023Member2019-12-310001126328pfg:PrincipalFinancialServicesIncAndPrincipalLifeInsuranceCompanyAndPrincipalFinancialGroupCoborrowersMemberpfg:CreditFacilityMaturingNovember2023Member2019-12-310001126328pfg:WMAdvisorsMember2020-12-310001126328pfg:WMAdvisorsMember2019-12-310001126328srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberpfg:AccountingStandardsUpdateAsu201616Member2017-12-312017-12-310001126328pfg:GuaranteesToUnconsolidatedTrustsUnderContingentFundingAgreementsMember2020-12-310001126328pfg:GuaranteesToThirdPartiesPrimarilyRelatedToFormerSubsidiariesAndJointVenturesMember2020-12-310001126328pfg:InstitutionalRetirementAndTrustBusinessOfWellsFargoBankMember2019-07-012019-07-010001126328pfg:SegmentUSInsuranceSolutionsMember2018-12-310001126328pfg:SegmentRetirementAndIncomeSolutionsMember2018-12-310001126328pfg:SegmentPrincipalInternationalMember2018-12-310001126328pfg:SegmentPrincipalGlobalInvestorsMember2018-12-310001126328pfg:SegmentCorporateMember2018-12-310001126328us-gaap:InterestRateContractMemberus-gaap:CashFlowHedgingMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:NetInvestmentHedgingMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:CashFlowHedgingMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310001126328us-gaap:NetInvestmentHedgingMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:CashFlowHedgingMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:CashFlowHedgingMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310001126328us-gaap:InterestRateContractMemberus-gaap:CashFlowHedgingMemberpfg:NetRealizedCapitalGainsLossesMember2020-01-012020-12-310001126328us-gaap:InterestRateContractMemberus-gaap:CashFlowHedgingMemberpfg:NetRealizedCapitalGainsLossesMember2019-01-012019-12-310001126328us-gaap:InterestRateContractMemberus-gaap:CashFlowHedgingMemberpfg:NetRealizedCapitalGainsLossesMember2018-01-012018-12-310001126328us-gaap:CashFlowHedgingMemberpfg:NetRealizedCapitalGainsLossesMember2020-01-012020-12-310001126328us-gaap:CashFlowHedgingMemberpfg:NetInvestmentIncomeLossMember2020-01-012020-12-310001126328us-gaap:CashFlowHedgingMemberpfg:BenefitsClaimsAndSettlementExpensesMember2020-01-012020-12-310001126328us-gaap:CashFlowHedgingMemberpfg:OperatingExpensesMember2019-01-012019-12-310001126328us-gaap:CashFlowHedgingMemberpfg:NetRealizedCapitalGainsLossesMember2019-01-012019-12-310001126328us-gaap:CashFlowHedgingMemberpfg:NetInvestmentIncomeLossMember2019-01-012019-12-310001126328us-gaap:CashFlowHedgingMemberpfg:BenefitsClaimsAndSettlementExpensesMember2019-01-012019-12-310001126328us-gaap:CashFlowHedgingMemberpfg:OperatingExpensesMember2018-01-012018-12-310001126328us-gaap:CashFlowHedgingMemberpfg:NetRealizedCapitalGainsLossesMember2018-01-012018-12-310001126328us-gaap:CashFlowHedgingMemberpfg:NetInvestmentIncomeLossMember2018-01-012018-12-310001126328us-gaap:CashFlowHedgingMemberpfg:BenefitsClaimsAndSettlementExpensesMember2018-01-012018-12-310001126328pfg:InstitutionalRetirementAndTrustBusinessOfWellsFargoBankMemberus-gaap:TechnologyBasedIntangibleAssetsMember2019-07-012019-07-010001126328pfg:InstitutionalRetirementAndTrustBusinessOfWellsFargoBankMemberus-gaap:CustomerRelationshipsMember2019-07-012019-07-010001126328us-gaap:CommercialRealEstatePortfolioSegmentMember2019-01-012019-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMember2018-01-012018-12-310001126328us-gaap:ResidentialMortgageMemberus-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember2020-12-310001126328us-gaap:ResidentialMortgageMemberus-gaap:FinancingReceivables60To89DaysPastDueMember2020-12-310001126328us-gaap:ResidentialMortgageMemberus-gaap:FinancingReceivables30To59DaysPastDueMember2020-12-310001126328us-gaap:FinanceLeasesPortfolioSegmentMemberus-gaap:FinancingReceivables60To89DaysPastDueMember2020-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMemberus-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember2020-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMemberus-gaap:FinancingReceivables60To89DaysPastDueMember2020-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMemberus-gaap:FinancingReceivables30To59DaysPastDueMember2020-12-310001126328us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember2020-12-310001126328us-gaap:FinancingReceivables60To89DaysPastDueMember2020-12-310001126328us-gaap:FinancingReceivables30To59DaysPastDueMember2020-12-310001126328us-gaap:HomeEquityMemberus-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember2019-12-310001126328us-gaap:HomeEquityMemberus-gaap:FinancingReceivables30To59DaysPastDueMember2019-12-310001126328us-gaap:FirstMortgageMemberus-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember2019-12-310001126328us-gaap:FirstMortgageMemberus-gaap:FinancingReceivables60To89DaysPastDueMember2019-12-310001126328us-gaap:FirstMortgageMemberus-gaap:FinancingReceivables30To59DaysPastDueMember2019-12-310001126328us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember2019-12-310001126328us-gaap:FinancingReceivables60To89DaysPastDueMember2019-12-310001126328us-gaap:FinancingReceivables30To59DaysPastDueMember2019-12-310001126328us-gaap:HomeEquityMember2019-12-310001126328pfg:CommercialCreditTenantMortgageMember2019-12-310001126328pfg:CommercialBrickAndMortarMortgageMember2019-12-310001126328us-gaap:FirstMortgageMember2019-12-310001126328pfg:StandardPoorsBPlusAndBelowRatingMemberus-gaap:FinanceLeasesPortfolioSegmentMember2020-12-310001126328pfg:StandardPoorsBPlusAndBelowRatingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:StandardPoorsBBPlusThruBBMinusRatingMemberus-gaap:FinanceLeasesPortfolioSegmentMember2020-12-310001126328pfg:StandardPoorsBBPlusThruBBMinusRatingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:StandardPoorsBBBPlusThruBBBMinusRatingMemberus-gaap:FinanceLeasesPortfolioSegmentMember2020-12-310001126328pfg:StandardPoorsBBBPlusThruBBBMinusRatingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:StandardPoorsAMinusAndAboveRatingMemberus-gaap:FinanceLeasesPortfolioSegmentMember2020-12-310001126328pfg:StandardPoorsAMinusAndAboveRatingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:PerformingMemberus-gaap:ResidentialMortgageMember2020-12-310001126328pfg:NonperformingMemberus-gaap:ResidentialMortgageMember2020-12-310001126328us-gaap:ResidentialMortgageMember2019-01-012019-12-310001126328us-gaap:ResidentialMortgageMember2018-01-012018-12-310001126328us-gaap:ResidentialMortgageMember2020-12-310001126328us-gaap:FinanceLeasesPortfolioSegmentMember2020-12-310001126328pfg:ReinsuranceRecoverablesMember2020-12-310001126328us-gaap:ResidentialMortgageMember2020-01-010001126328us-gaap:CommercialRealEstatePortfolioSegmentMember2020-01-010001126328pfg:ReinsuranceRecoverablesMember2020-01-0100011263282020-01-010001126328us-gaap:ResidentialMortgageMember2019-12-310001126328us-gaap:ResidentialMortgageMember2018-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMember2018-12-310001126328us-gaap:ResidentialMortgageMember2017-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMember2017-12-310001126328us-gaap:EquityMethodInvestmentsMember2020-01-012020-12-310001126328us-gaap:EquityMethodInvestmentsMember2019-01-012019-12-310001126328pfg:CommercialMortgageLoansOfConsolidatedVariableInterestEntitiesMember2019-01-012019-12-310001126328us-gaap:EquityMethodInvestmentsMember2018-01-012018-12-310001126328pfg:CommercialMortgageLoansOfConsolidatedVariableInterestEntitiesMember2018-01-012018-12-310001126328us-gaap:FairValueMeasurementsRecurringMember2018-12-310001126328us-gaap:FairValueMeasurementsRecurringMember2017-12-310001126328pfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328pfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328pfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2018-12-310001126328pfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2017-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:TradingSecuritiesMember2019-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-12-310001126328us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueMeasurementsRecurringMember2018-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueMeasurementsRecurringMember2018-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2017-12-310001126328us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2017-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2017-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2017-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2017-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2017-12-310001126328us-gaap:EquitySecuritiesMemberus-gaap:FairValueMeasurementsRecurringMember2017-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueMeasurementsRecurringMember2017-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueMeasurementsRecurringMember2017-12-310001126328us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-01-012019-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:TradingSecuritiesMember2019-01-012019-12-310001126328us-gaap:EquitySecuritiesMemberus-gaap:FairValueMeasurementsRecurringMember2018-01-012018-12-310001126328us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310001126328us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310001126328us-gaap:EmployeeStockOptionMember2019-01-012019-12-310001126328us-gaap:EmployeeStockOptionMember2018-01-012018-12-310001126328us-gaap:EmployeeStockOptionMember2020-01-012020-12-310001126328us-gaap:RestrictedStockUnitsRSUMember2020-12-310001126328us-gaap:PerformanceSharesMember2020-12-310001126328us-gaap:EmployeeStockOptionMember2020-12-310001126328us-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328us-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputPriceVolatilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLapseRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputNonPerformanceRiskMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLongDurationInterestRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputPriceVolatilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLapseRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputNonPerformanceRiskMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLongDurationInterestRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputPriceVolatilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLapseRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputNonPerformanceRiskMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLongDurationInterestRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputPriceVolatilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MinimumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLapseRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MinimumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputNonPerformanceRiskMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MinimumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLongDurationInterestRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MaximumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputPriceVolatilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MaximumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLapseRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MaximumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputNonPerformanceRiskMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MaximumMemberus-gaap:FairValueInputsLevel3Memberpfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLongDurationInterestRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328pfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsSpreadMember2020-01-012020-12-310001126328pfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2020-01-012020-12-310001126328us-gaap:SwaptionMember2020-12-310001126328us-gaap:SingleStockFutureMember2020-12-310001126328us-gaap:EmbeddedDerivativeFinancialInstrumentsMember2020-12-310001126328pfg:InterestRateFutureMember2020-12-310001126328us-gaap:SwaptionMember2019-12-310001126328us-gaap:SingleStockFutureMember2019-12-310001126328us-gaap:EmbeddedDerivativeFinancialInstrumentsMember2019-12-310001126328pfg:InterestRateFutureMember2019-12-310001126328us-gaap:OtherContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2020-12-310001126328us-gaap:InterestRateContractMemberus-gaap:DesignatedAsHedgingInstrumentMember2020-12-310001126328us-gaap:OtherContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2019-12-310001126328us-gaap:InterestRateContractMemberus-gaap:DesignatedAsHedgingInstrumentMember2019-12-310001126328us-gaap:OtherContractMember2020-01-012020-12-310001126328us-gaap:InterestRateContractMember2020-01-012020-12-310001126328us-gaap:ForeignExchangeContractMember2020-01-012020-12-310001126328us-gaap:EquityContractMember2020-01-012020-12-310001126328us-gaap:CreditRiskContractMember2020-01-012020-12-310001126328us-gaap:OtherContractMember2019-01-012019-12-310001126328us-gaap:InterestRateContractMember2019-01-012019-12-310001126328us-gaap:ForeignExchangeContractMember2019-01-012019-12-310001126328us-gaap:EquityContractMember2019-01-012019-12-310001126328us-gaap:CreditRiskContractMember2019-01-012019-12-310001126328us-gaap:OtherContractMember2018-01-012018-12-310001126328us-gaap:InterestRateContractMember2018-01-012018-12-310001126328us-gaap:ForeignExchangeContractMember2018-01-012018-12-310001126328us-gaap:EquityContractMember2018-01-012018-12-310001126328us-gaap:CreditRiskContractMember2018-01-012018-12-310001126328us-gaap:InterestRateContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2020-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2020-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMember2020-12-310001126328us-gaap:EquityContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2020-12-310001126328us-gaap:CreditRiskContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2020-12-310001126328us-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2020-12-310001126328us-gaap:DesignatedAsHedgingInstrumentMember2020-12-310001126328us-gaap:InterestRateContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2019-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2019-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMember2019-12-310001126328us-gaap:EquityContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2019-12-310001126328us-gaap:CreditRiskContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2019-12-310001126328us-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2019-12-310001126328us-gaap:DesignatedAsHedgingInstrumentMember2019-12-310001126328pfg:SegmentCorporateMember2020-01-012020-12-310001126328pfg:SegmentCorporateMember2019-01-012019-12-310001126328pfg:SegmentCorporateMember2018-01-012018-12-310001126328us-gaap:QualifiedPlanMemberpfg:DefinedContributionPlanGeneralParticipantMember2020-01-012020-12-310001126328us-gaap:NonqualifiedPlanMemberpfg:DefinedContributionPlanGrandfatheredChoiceParticipantMember2020-01-012020-12-310001126328us-gaap:NonqualifiedPlanMemberpfg:DefinedContributionPlanGeneralParticipantMember2020-01-012020-12-310001126328srt:MinimumMemberus-gaap:FixedIncomeSecuritiesMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328srt:MinimumMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328srt:MaximumMemberus-gaap:FixedIncomeSecuritiesMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328srt:MaximumMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:AlternativesMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:FixedIncomeSecuritiesMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueInputsLevel1Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:HedgeFundsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:SingleClientSeparateAccountsInvestedInPooledSeparateAccountMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:OtherPlanAssetsMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:DefinedBenefitPlanEquitySecuritiesUsSmallMidCapMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:BalancedAssetAllocationPortfoliosMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:USTreasuryAndGovernmentMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:USStatesAndPoliticalSubdivisionsMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:OtherDebtSecuritiesMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:HedgeFundsMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanRealEstateMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:CorporateDebtSecuritiesMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:SingleClientSeparateAccountsInvestedInPooledSeparateAccountMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:OtherPlanAssetsMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:DefinedBenefitPlanEquitySecuritiesUsSmallMidCapMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328pfg:BalancedAssetAllocationPortfoliosMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:FixedIncomeFundsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:FixedIncomeFundsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:FixedIncomeFundsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310001126328us-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueInputsLevel1Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:HedgeFundsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:SingleClientSeparateAccountsInvestedInPooledSeparateAccountMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:OtherPlanAssetsMemberus-gaap:FairValueInputsLevel2Memberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:DefinedBenefitPlanEquitySecuritiesUsSmallMidCapMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:BalancedAssetAllocationPortfoliosMemberus-gaap:FairValueInputsLevel2Memberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:USTreasuryAndGovernmentMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:USStatesAndPoliticalSubdivisionsMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:OtherDebtSecuritiesMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:HedgeFundsMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanRealEstateMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:CorporateDebtSecuritiesMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:SingleClientSeparateAccountsInvestedInPooledSeparateAccountMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:OtherPlanAssetsMemberpfg:SingleClientSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:DefinedBenefitPlanEquitySecuritiesUsSmallMidCapMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:BalancedAssetAllocationPortfoliosMemberpfg:PooledSeparateAccountInvestmentsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:FixedIncomeFundsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:FixedIncomeFundsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:FixedIncomeFundsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310001126328srt:MaximumMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:PensionPlansDefinedBenefitMember2018-12-310001126328us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-12-310001126328pfg:PensionPlansDefinedBenefitTraditionalBenefitMember2020-01-012020-12-310001126328pfg:PensionPlansDefinedBenefitCashBalanceBenefitMember2020-01-012020-12-310001126328pfg:PensionPlansDefinedBenefitTraditionalBenefitMember2019-01-012019-12-310001126328pfg:PensionPlansDefinedBenefitCashBalanceBenefitMember2019-01-012019-12-310001126328pfg:PensionPlansDefinedBenefitTraditionalBenefitMember2018-01-012018-12-310001126328pfg:PensionPlansDefinedBenefitCashBalanceBenefitMember2018-01-012018-12-310001126328pfg:Post65MedicalPlansMember2020-01-012020-12-310001126328pfg:HomeOfficeMedicalAndLifePlansMember2020-01-012020-12-310001126328pfg:AgentMedicalAndLifePlanMember2020-01-012020-12-310001126328us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-04-012020-12-310001126328us-gaap:PensionPlansDefinedBenefitMember2019-06-012019-12-310001126328us-gaap:PensionPlansDefinedBenefitMember2019-01-012019-05-310001126328pfg:PensionPlansDefinedBenefitTraditionalBenefitMember2020-12-310001126328pfg:PensionPlansDefinedBenefitCashBalanceBenefitMember2020-12-310001126328pfg:PensionPlansDefinedBenefitTraditionalBenefitMember2019-12-310001126328pfg:PensionPlansDefinedBenefitCashBalanceBenefitMember2019-12-310001126328us-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310001126328us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-01-012018-12-310001126328us-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:NonqualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310001126328us-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328us-gaap:NonqualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310001126328pfg:SegmentUSInsuranceSolutionsMember2020-01-012020-12-310001126328pfg:SegmentPrincipalInternationalMember2020-01-012020-12-310001126328pfg:SegmentUSInsuranceSolutionsMember2019-01-012019-12-310001126328pfg:SegmentPrincipalInternationalMember2019-01-012019-12-310001126328pfg:SegmentUSInsuranceSolutionsMember2018-01-012018-12-310001126328pfg:SegmentPrincipalInternationalMember2018-01-012018-12-310001126328us-gaap:DomesticCountryMember2020-12-310001126328us-gaap:DomesticCountryMember2019-12-310001126328us-gaap:StateAndLocalJurisdictionMember2020-12-310001126328us-gaap:ForeignCountryMember2020-12-310001126328us-gaap:StateAndLocalJurisdictionMember2019-12-310001126328us-gaap:ForeignCountryMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputComparabilityAdjustmentMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MinimumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputComparabilityAdjustmentMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:MaximumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputComparabilityAdjustmentMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2020-12-310001126328srt:WeightedAverageMemberus-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:WeightedAverageMemberus-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MinimumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MinimumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MinimumMemberus-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MaximumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MaximumMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328srt:MaximumMemberus-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputLossSeverityMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:MeasurementInputDefaultRateMemberus-gaap:ValuationTechniqueDiscountedCashFlowMember2019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMember2020-01-012020-12-310001126328us-gaap:CollateralizedDebtObligationsMember2020-01-012020-12-310001126328pfg:PrincipalInternationalChileMembersrt:MaximumMemberpfg:UnsecuredLineOfCreditMember2020-01-012020-12-310001126328pfg:PrincipalInternationalChileMembersrt:MaximumMemberpfg:UnsecuredLineOfCreditMember2019-01-012019-12-310001126328srt:MinimumMemberpfg:NonRecourseMortgagesAndNotesPayableConsolidateMember2020-12-310001126328srt:MaximumMemberpfg:NonRecourseMortgagesAndNotesPayableConsolidateMember2020-12-310001126328srt:MinimumMemberpfg:NonRecourseMortgagesAndNotesPayableConsolidateMember2019-12-310001126328srt:MaximumMemberpfg:NonRecourseMortgagesAndNotesPayableConsolidateMember2019-12-310001126328pfg:Delaware2048TrustMemberpfg:SeniorNotesDue2048Memberpfg:ContingentFundingAgreement30YearMember2018-03-080001126328pfg:Delaware2028TrustMemberpfg:SeniorNotesDue2028Memberpfg:ContingentFundingAgreement10YearMember2018-03-080001126328pfg:NotesPayable2.125PercentDue2030Memberus-gaap:SeniorNotesMember2020-08-030001126328pfg:NotesPayable2.125PercentDue2030Memberus-gaap:SeniorNotesMember2020-06-120001126328pfg:NotesPayable3.7PercentDue2029Memberus-gaap:SeniorNotesMember2019-05-070001126328pfg:NotesPayable4.3PercentDue2046Memberus-gaap:SeniorNotesMember2016-11-100001126328pfg:NotesPayable3.1PercentDue2026Memberus-gaap:SeniorNotesMember2016-11-100001126328pfg:NotesPayable3.1PercentDue2026AndNotesPayable4.3PercentDue2046Memberus-gaap:SeniorNotesMember2016-11-100001126328pfg:NotesPayable4.7PercentDue2055Memberus-gaap:JuniorSubordinatedDebtMember2015-05-070001126328pfg:NotesPayable3.4PercentDue2025Memberus-gaap:SeniorNotesMember2015-05-070001126328pfg:NotesPayable4.35PercentDue2043Memberus-gaap:SeniorNotesMember2012-11-160001126328pfg:NotesPayable3.125PercentDue2023Memberus-gaap:SeniorNotesMember2012-11-160001126328pfg:NotesPayable1.85PercentDue2017Memberus-gaap:SeniorNotesMember2012-11-160001126328pfg:NotesPayable1.85PercentDue2017And3.125PercentDue2023And4.35PercentDue2043Memberus-gaap:SeniorNotesMember2012-11-160001126328pfg:NotesPayable4.625PercentDue2042Memberus-gaap:SeniorNotesMember2012-09-050001126328pfg:NotesPayable3.3PercentDue2022Memberus-gaap:SeniorNotesMember2012-09-050001126328pfg:NotesPayable3.3PercentDue2022And4.625PercentDue2042Memberus-gaap:SeniorNotesMember2012-09-050001126328pfg:NotesPayable8.875PercentDue2019Memberus-gaap:SeniorNotesMember2009-05-180001126328pfg:NotesPayable7.875PercentDue2014Memberus-gaap:SeniorNotesMember2009-05-180001126328pfg:NotesPayable7.875PercentDue2014And8.875PercentDue2019Memberus-gaap:SeniorNotesMember2009-05-180001126328pfg:NotesPayable6.05PercentDue2036IssuedDecember2006Memberus-gaap:SeniorNotesMember2006-12-050001126328pfg:NotesPayable6.05PercentDue2036IssuedOctober2006Memberus-gaap:SeniorNotesMember2006-10-160001126328pfg:NotesPayableFloatingRateDue2055Member2020-12-310001126328pfg:NotesPayable6.05PercentDue2036Member2020-12-310001126328pfg:NotesPayable4.625PercentDue2042Member2020-12-310001126328pfg:NotesPayable4.3PercentDue2046Member2020-12-310001126328pfg:NotesPayable4.35PercentDue2043Member2020-12-310001126328pfg:NotesPayable3.7PercentDue2029Member2020-12-310001126328pfg:NotesPayable3.4PercentDue2025Member2020-12-310001126328pfg:NotesPayable3.3PercentDue2022Member2020-12-310001126328pfg:NotesPayable3.1PercentDue2026Member2020-12-310001126328pfg:NotesPayable3.125PercentDue2023Member2020-12-310001126328pfg:NotesPayable2.125PercentDue2030Member2020-12-310001126328pfg:NotesPayable6.05PercentDue2036Member2019-12-310001126328pfg:NotesPayable4.7PercentDue2055Member2019-12-310001126328pfg:NotesPayable4.625PercentDue2042Member2019-12-310001126328pfg:NotesPayable4.3PercentDue2046Member2019-12-310001126328pfg:NotesPayable4.35PercentDue2043Member2019-12-310001126328pfg:NotesPayable3.7PercentDue2029Member2019-12-310001126328pfg:NotesPayable3.4PercentDue2025Member2019-12-310001126328pfg:NotesPayable3.3PercentDue2022Member2019-12-310001126328pfg:NotesPayable3.1PercentDue2026Member2019-12-310001126328pfg:NotesPayable3.125PercentDue2023Member2019-12-310001126328pfg:NotesPayable4.7PercentDue2055Memberus-gaap:JuniorSubordinatedDebtMember2015-05-072015-05-070001126328us-gaap:CommonStockMember2020-01-012020-12-310001126328us-gaap:CommonStockMember2019-01-012019-12-310001126328us-gaap:CommonStockMember2018-01-012018-12-310001126328us-gaap:InterestRateContractMemberus-gaap:FairValueHedgingMemberpfg:NetRealizedCapitalGainsLossesMember2018-01-012018-12-310001126328us-gaap:AccidentAndHealthInsuranceSegmentMember2020-01-012020-12-310001126328us-gaap:AccidentAndHealthInsuranceSegmentMember2019-01-012019-12-310001126328us-gaap:AccidentAndHealthInsuranceSegmentMember2018-01-012018-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2018-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2018-12-310001126328pfg:SubsidiaryPrincipalFinancialServicesConsolidateMembersrt:ReportableLegalEntitiesMember2018-12-310001126328pfg:SubsidiariesPrincipalLifeInsuranceAndOtherConsolidateMembersrt:ReportableLegalEntitiesMember2018-12-310001126328pfg:ConsolidationEliminationsAndOtherShelfRegistrationDebtGuarantorMembersrt:ConsolidationEliminationsMember2018-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2017-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2017-12-310001126328pfg:SubsidiaryPrincipalFinancialServicesConsolidateMembersrt:ReportableLegalEntitiesMember2017-12-310001126328pfg:SubsidiariesPrincipalLifeInsuranceAndOtherConsolidateMembersrt:ReportableLegalEntitiesMember2017-12-310001126328pfg:ConsolidationEliminationsAndOtherShelfRegistrationDebtGuarantorMembersrt:ConsolidationEliminationsMember2017-12-3100011263282017-12-3100011263282020-10-012020-12-3100011263282020-07-012020-09-3000011263282020-04-012020-06-3000011263282020-01-012020-03-3100011263282019-10-012019-12-3100011263282019-07-012019-09-3000011263282019-04-012019-06-3000011263282019-01-012019-03-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:OtherDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CorporateDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CollateralizedDebtObligationsMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasuryAndGovernmentMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:OtherDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CorporateDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CollateralizedDebtObligationsMember2020-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasuryAndGovernmentMember2020-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasuryAndGovernmentMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:OtherDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:CorporateDebtSecuritiesMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:CollateralizedDebtObligationsMember2020-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:OtherDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CorporateDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CollateralizedDebtObligationsMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasuryAndGovernmentMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:OtherDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CorporateDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CollateralizedDebtObligationsMember2019-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasuryAndGovernmentMember2019-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CorporateDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasuryAndGovernmentMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:OtherDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:CorporateDebtSecuritiesMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMemberus-gaap:CollateralizedDebtObligationsMember2019-12-310001126328us-gaap:USTreasuryAndGovernmentMember2020-12-310001126328us-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310001126328us-gaap:ResidentialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:OtherDebtSecuritiesMember2020-12-310001126328us-gaap:ForeignGovernmentDebtSecuritiesMember2020-12-310001126328us-gaap:CorporateDebtSecuritiesMember2020-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:CollateralizedDebtObligationsMember2020-12-310001126328us-gaap:USTreasuryAndGovernmentMember2019-12-310001126328us-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310001126328us-gaap:ResidentialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:ForeignGovernmentDebtSecuritiesMember2019-12-310001126328us-gaap:CorporateDebtSecuritiesMember2019-12-310001126328us-gaap:LifeAndAnnuityInsuranceProductLineMember2020-01-012020-12-310001126328us-gaap:LifeAndAnnuityInsuranceProductLineMember2019-01-012019-12-310001126328us-gaap:LifeAndAnnuityInsuranceProductLineMember2018-01-012018-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:OtherDebtSecuritiesMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:CorporateDebtSecuritiesMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:CollateralizedDebtObligationsMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:TradingSecuritiesMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:TradingSecuritiesMemberus-gaap:OtherDebtSecuritiesMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:TradingSecuritiesMemberus-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:TradingSecuritiesMemberus-gaap:CollateralizedDebtObligationsMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:EquitySecuritiesMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:OtherLimitedPartnershipAndFundInterestsMember2020-12-310001126328us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember2020-12-310001126328pfg:VariableInterestEntityPrimaryBeneficiarySponsoredInvestmentFundsMember2020-12-310001126328pfg:VariableInterestEntityPrimaryBeneficiaryResidentialMortgageLoansMember2020-12-310001126328pfg:VariableInterestEntityPrimaryBeneficiaryRealEstateMember2020-12-310001126328pfg:VariableInterestEntityPrimaryBeneficiaryMandatoryRetirementSavingsMember2020-12-310001126328pfg:SegmentPrincipalGlobalInvestorsMember2020-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:OtherDebtSecuritiesMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:CorporateDebtSecuritiesMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:CollateralizedDebtObligationsMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:TradingSecuritiesMemberus-gaap:ResidentialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:TradingSecuritiesMemberus-gaap:OtherDebtSecuritiesMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:TradingSecuritiesMemberus-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:TradingSecuritiesMemberus-gaap:CollateralizedDebtObligationsMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberus-gaap:EquitySecuritiesMember2019-12-310001126328us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberpfg:OtherLimitedPartnershipAndFundInterestsMember2019-12-310001126328us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember2019-12-310001126328pfg:VariableInterestEntityPrimaryBeneficiarySponsoredInvestmentFundsMember2019-12-310001126328pfg:VariableInterestEntityPrimaryBeneficiaryRealEstateMember2019-12-310001126328pfg:VariableInterestEntityPrimaryBeneficiaryMandatoryRetirementSavingsMember2019-12-310001126328pfg:VariableInterestEntityPrimaryBeneficiaryGrantorTrustsMember2019-12-310001126328pfg:SegmentPrincipalGlobalInvestorsMember2019-12-310001126328us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2020-12-310001126328us-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310001126328us-gaap:OtherIntangibleAssetsMember2020-01-012020-12-310001126328pfg:ConsolidationEliminationsAndOtherShelfRegistrationDebtGuarantorMembersrt:ConsolidationEliminationsMember2020-12-310001126328pfg:ConsolidationEliminationsAndOtherShelfRegistrationDebtGuarantorMembersrt:ConsolidationEliminationsMember2019-12-310001126328srt:MaximumMemberus-gaap:JuniorSubordinatedDebtMember2015-05-072015-05-070001126328pfg:OtherLimitedPartnershipAndFundInterestsMember2020-12-310001126328pfg:OtherLimitedPartnershipAndFundInterestsMember2019-12-310001126328us-gaap:CommonStockMember2020-02-012020-02-290001126328us-gaap:CommonStockMember2018-11-012018-11-300001126328us-gaap:CommonStockMember2018-05-012018-05-310001126328us-gaap:CommonStockMember2017-05-012017-05-310001126328us-gaap:CommonStockMember2016-02-012016-02-290001126328pfg:ContingentFundingAgreementMember2018-03-0800011263282017-01-012017-12-310001126328us-gaap:RetainedEarningsMember2020-01-012020-12-310001126328us-gaap:RetainedEarningsMember2019-01-012019-12-310001126328us-gaap:RetainedEarningsMember2018-01-012018-12-310001126328pfg:StockBasedCompensationPlansMember2020-01-012020-12-310001126328pfg:StockBasedCompensationPlansMember2019-01-012019-12-310001126328pfg:StockBasedCompensationPlansMember2018-01-012018-12-310001126328pfg:StockBasedCompensationPlan2014DirectorsStockPlanMember2020-05-190001126328pfg:StockBasedCompensationPlansAmendedAndRestated2010StockIncentivePlan2005DirectorsStockPlanMember2014-05-200001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLongTermRevenueGrowthRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowMortgageLoansMember2020-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberpfg:DiscountedCashFlowMortgageLoansMember2020-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputCreditSpreadMemberpfg:DiscountedCashFlowMortgageLoansMember2020-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputTerminalCapitalizationRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputMarketInterestRateMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLoanToValueRatioMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLongTermRevenueGrowthRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputTerminalCapitalizationRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputMarketInterestRateMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLoanToValueRatioMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLongTermRevenueGrowthRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputTerminalCapitalizationRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputMarketInterestRateMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLoanToValueRatioMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowMortgageLoansMember2020-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberpfg:DiscountedCashFlowMortgageLoansMember2020-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputCreditSpreadMemberpfg:DiscountedCashFlowMortgageLoansMember2020-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLongTermRevenueGrowthRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowMortgageLoansMember2019-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberpfg:DiscountedCashFlowMortgageLoansMember2019-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputCreditSpreadMemberpfg:DiscountedCashFlowMortgageLoansMember2019-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputTerminalCapitalizationRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputMarketInterestRateMemberpfg:DiscountedCashFlowRealEstateDebtMember2019-12-310001126328srt:WeightedAverageMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLoanToValueRatioMemberpfg:DiscountedCashFlowRealEstateDebtMember2019-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLongTermRevenueGrowthRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputTerminalCapitalizationRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputMarketInterestRateMemberpfg:DiscountedCashFlowRealEstateDebtMember2019-12-310001126328srt:MinimumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLoanToValueRatioMemberpfg:DiscountedCashFlowRealEstateDebtMember2019-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLongTermRevenueGrowthRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputTerminalCapitalizationRateMemberpfg:DiscountedCashFlowRealEstateMember2019-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputMarketInterestRateMemberpfg:DiscountedCashFlowRealEstateDebtMember2019-12-310001126328srt:MaximumMemberpfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLoanToValueRatioMemberpfg:DiscountedCashFlowRealEstateDebtMember2019-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowMortgageLoansMember2019-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberpfg:DiscountedCashFlowMortgageLoansMember2019-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputCreditSpreadMemberpfg:DiscountedCashFlowMortgageLoansMember2019-12-310001126328pfg:LongTermDisabilityGroupLifeWaiverMember2020-12-310001126328pfg:GroupLifeMember2020-12-310001126328pfg:Delaware2048TrustMember2018-03-082018-03-080001126328pfg:Delaware2028TrustMember2018-03-082018-03-080001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMemberus-gaap:NonqualifiedPlanMember2020-12-310001126328pfg:SubsidiariesPrincipalLifeInsuranceAndOtherConsolidateMembersrt:ReportableLegalEntitiesMemberus-gaap:NonqualifiedPlanMember2020-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMemberus-gaap:NonqualifiedPlanMember2019-12-310001126328pfg:SubsidiariesPrincipalLifeInsuranceAndOtherConsolidateMembersrt:ReportableLegalEntitiesMemberus-gaap:NonqualifiedPlanMember2019-12-310001126328us-gaap:InterestRateContractMemberus-gaap:FairValueHedgingMemberpfg:NetInvestmentIncomeLossMember2020-01-012020-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:CashFlowHedgingMemberpfg:NetInvestmentIncomeLossMember2020-01-012020-12-310001126328us-gaap:InterestRateContractMemberus-gaap:FairValueHedgingMemberpfg:NetInvestmentIncomeLossMember2019-01-012019-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:CashFlowHedgingMemberpfg:NetInvestmentIncomeLossMember2019-01-012019-12-310001126328us-gaap:InterestRateContractMemberus-gaap:FairValueHedgingMemberpfg:NetInvestmentIncomeLossMember2018-01-012018-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:CashFlowHedgingMemberpfg:NetInvestmentIncomeLossMember2018-01-012018-12-310001126328us-gaap:ForeignExchangeContractMemberus-gaap:CashFlowHedgingMemberpfg:BenefitsClaimsAndSettlementExpensesMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberus-gaap:FinancialServiceOtherMemberpfg:SegmentPrincipalGlobalInvestorsMember2018-07-012018-09-300001126328pfg:Delaware2028TrustMemberpfg:ContingentFundingAgreement10YearMember2018-03-082018-03-080001126328srt:RetailSiteMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328srt:OtherPropertyMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328srt:OfficeBuildingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328srt:IndustrialPropertyMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328srt:HotelMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328srt:ApartmentBuildingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:WestSouthCentralMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:WestNorthCentralMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:SouthAtlanticMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:PacificMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:NewEnglandMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:MountainMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:MiddleAtlanticMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:InternationalMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:EastSouthCentralMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328pfg:EastNorthCentralMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMember2020-12-310001126328srt:RetailSiteMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328srt:OtherPropertyMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328srt:OfficeBuildingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328srt:IndustrialPropertyMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328srt:HotelMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328srt:ApartmentBuildingMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:WestSouthCentralMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:WestNorthCentralMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:SouthAtlanticMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:PacificMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:NewEnglandMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:MountainMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:MiddleAtlanticMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:InternationalMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:EastSouthCentralMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:EastNorthCentralMemberus-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMember2019-12-310001126328pfg:Delaware2048TrustMemberpfg:ContingentFundingAgreement30YearMember2018-03-082018-03-080001126328pfg:SubsegmentIndividualLifeInsuranceMember2020-12-310001126328pfg:SubsegmentIndividualLifeInsuranceMember2019-12-310001126328pfg:SubsegmentIndividualLifeInsuranceMember2018-12-310001126328us-gaap:OtherDebtSecuritiesMember2019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310001126328us-gaap:CollateralizedDebtObligationsMember2019-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2020-12-310001126328pfg:SubsidiaryPrincipalFinancialServicesConsolidateMembersrt:ReportableLegalEntitiesMember2020-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2019-12-310001126328pfg:SubsidiaryPrincipalFinancialServicesConsolidateMembersrt:ReportableLegalEntitiesMember2019-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLongTermRevenueGrowthRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2020-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputCreditSpreadMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:TerminalEarningsBeforeInterestTaxesDepreciationAndAmortizationMultipleMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2020-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:RevenueMultiplesMemberus-gaap:MarketApproachValuationTechniqueMember2020-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputTerminalCapitalizationRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLoanToValueRatioMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328srt:MinimumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2020-12-310001126328srt:MinimumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:TerminalEarningsBeforeInterestTaxesDepreciationAndAmortizationMultipleMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2020-12-310001126328srt:MinimumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:RevenueMultiplesMemberus-gaap:MarketApproachValuationTechniqueMember2020-12-310001126328srt:MaximumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2020-12-310001126328srt:MaximumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:TerminalEarningsBeforeInterestTaxesDepreciationAndAmortizationMultipleMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2020-12-310001126328srt:MaximumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:RevenueMultiplesMemberus-gaap:MarketApproachValuationTechniqueMember2020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputLongTermRevenueGrowthRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputCreditSpreadMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputTerminalCapitalizationRateMemberpfg:DiscountedCashFlowRealEstateMember2020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:MeasurementInputLoanToValueRatioMemberpfg:DiscountedCashFlowRealEstateDebtMember2020-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2019-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:TerminalEarningsBeforeInterestTaxesDepreciationAndAmortizationMultipleMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2019-12-310001126328srt:WeightedAverageMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:RevenueMultiplesMemberus-gaap:MarketApproachValuationTechniqueMember2019-12-310001126328srt:MinimumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2019-12-310001126328srt:MinimumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:TerminalEarningsBeforeInterestTaxesDepreciationAndAmortizationMultipleMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2019-12-310001126328srt:MinimumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:RevenueMultiplesMemberus-gaap:MarketApproachValuationTechniqueMember2019-12-310001126328srt:MaximumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MeasurementInputDiscountRateMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2019-12-310001126328srt:MaximumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:TerminalEarningsBeforeInterestTaxesDepreciationAndAmortizationMultipleMemberpfg:ValuationTechniqueDiscountedCashFlowOtherInvestmentsMember2019-12-310001126328srt:MaximumMemberpfg:InvestmentsOtherMemberus-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMemberpfg:RevenueMultiplesMemberus-gaap:MarketApproachValuationTechniqueMember2019-12-310001126328us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310001126328us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310001126328us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2020-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentEliminationsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentEliminationsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentEliminationsMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMember2018-01-012018-12-310001126328us-gaap:InterestRateContractMemberus-gaap:CashFlowHedgingMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310001126328us-gaap:InterestRateContractMemberus-gaap:CashFlowHedgingMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310001126328pfg:ContingentFundingAgreementMember2018-03-082018-03-080001126328us-gaap:FairValueInputsLevel3Memberus-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310001126328us-gaap:RestrictedStockUnitsRSUMember2020-01-012020-12-310001126328us-gaap:PerformanceSharesMember2020-01-012020-12-310001126328us-gaap:RestrictedStockUnitsRSUMember2019-01-012019-12-310001126328us-gaap:PerformanceSharesMember2019-01-012019-12-310001126328us-gaap:RestrictedStockUnitsRSUMember2018-01-012018-12-310001126328us-gaap:PerformanceSharesMember2018-01-012018-12-310001126328pfg:SegmentRetirementAndIncomeSolutionsMember2020-01-012020-12-310001126328pfg:SegmentPrincipalGlobalInvestorsMember2020-01-012020-12-310001126328pfg:SegmentRetirementAndIncomeSolutionsMember2019-01-012019-12-310001126328pfg:SegmentPrincipalGlobalInvestorsMember2019-01-012019-12-310001126328pfg:SegmentRetirementAndIncomeSolutionsMember2018-01-012018-12-310001126328pfg:SegmentPrincipalGlobalInvestorsMember2018-01-012018-12-310001126328us-gaap:InterestRateSwapMember2020-01-012020-12-310001126328pfg:FixedMaturitiesSecuritiesAvailableForSaleMember2020-12-310001126328pfg:FixedMaturitiesSecuritiesAvailableForSaleMember2019-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:DebtSecuritiesMember2020-01-012020-12-310001126328pfg:TradingSecuritiesMemberus-gaap:DebtSecuritiesMember2020-01-012020-12-310001126328us-gaap:PolicyLoansMember2020-01-012020-12-310001126328us-gaap:EquitySecuritiesMember2020-01-012020-12-310001126328us-gaap:DerivativeMember2020-01-012020-12-310001126328us-gaap:CashAndCashEquivalentsMember2020-01-012020-12-310001126328pfg:OtherInvestmentTypesMember2020-01-012020-12-310001126328pfg:MortgageLoansMember2020-01-012020-12-310001126328pfg:InvestmentsInRealEstateMember2020-01-012020-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:DebtSecuritiesMember2019-01-012019-12-310001126328pfg:TradingSecuritiesMemberus-gaap:DebtSecuritiesMember2019-01-012019-12-310001126328us-gaap:PolicyLoansMember2019-01-012019-12-310001126328us-gaap:EquitySecuritiesMember2019-01-012019-12-310001126328us-gaap:DerivativeMember2019-01-012019-12-310001126328us-gaap:CashAndCashEquivalentsMember2019-01-012019-12-310001126328pfg:OtherInvestmentTypesMember2019-01-012019-12-310001126328pfg:MortgageLoansMember2019-01-012019-12-310001126328pfg:InvestmentsInRealEstateMember2019-01-012019-12-310001126328us-gaap:AvailableforsaleSecuritiesMemberus-gaap:DebtSecuritiesMember2018-01-012018-12-310001126328pfg:TradingSecuritiesMemberus-gaap:DebtSecuritiesMember2018-01-012018-12-310001126328us-gaap:PolicyLoansMember2018-01-012018-12-310001126328us-gaap:EquitySecuritiesMember2018-01-012018-12-310001126328us-gaap:DerivativeMember2018-01-012018-12-310001126328us-gaap:CashAndCashEquivalentsMember2018-01-012018-12-310001126328pfg:OtherInvestmentTypesMember2018-01-012018-12-310001126328pfg:MortgageLoansMember2018-01-012018-12-310001126328pfg:InvestmentsInRealEstateMember2018-01-012018-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMember2020-01-012020-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2011ProgramMember2011-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2006ProgramMember2006-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2004ProgramMember2004-03-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2001ProgramMember2001-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement1998ProgramMember1998-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2011ProgramMember2017-11-300001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2011ProgramMember2015-06-300001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreementsFederalHomeLoanBankDesMoinesMember2020-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2011ProgramMember2020-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2006ProgramMember2020-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2001ProgramMember2020-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement1998ProgramMember2020-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2004ProgramMember2020-04-300001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreementsFederalHomeLoanBankDesMoinesMember2019-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2011ProgramMember2019-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2006ProgramMember2019-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2004ProgramMember2019-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement2001ProgramMember2019-12-310001126328pfg:PrincipalLifeInsuranceCompanyConsolidatedMemberpfg:FundingAgreement1998ProgramMember2019-12-310001126328us-gaap:ResidentialMortgageMember2020-01-022020-12-310001126328us-gaap:CommercialRealEstatePortfolioSegmentMember2020-01-022020-12-3100011263282020-01-022020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentSpecialtyBenefitsInsuranceMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsSpreadMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentPrincipalInternationalMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentPrincipalGlobalInvestorsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentCorporateMember2020-01-012020-12-310001126328us-gaap:MaterialReconcilingItemsMember2020-01-012020-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentSpecialtyBenefitsInsuranceMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsSpreadMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentPrincipalInternationalMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentPrincipalGlobalInvestorsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentCorporateMember2019-01-012019-12-310001126328us-gaap:MaterialReconcilingItemsMember2019-01-012019-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentSpecialtyBenefitsInsuranceMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentUSInsuranceSolutionsMemberpfg:SubsegmentIndividualLifeInsuranceMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsSpreadMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentRetirementAndIncomeSolutionsMemberpfg:SubsegmentRetirementAndIncomeSolutionsFeeMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentPrincipalInternationalMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentPrincipalGlobalInvestorsMember2018-01-012018-12-310001126328us-gaap:OperatingSegmentsMemberpfg:SegmentCorporateMember2018-01-012018-12-310001126328us-gaap:MaterialReconcilingItemsMember2018-01-012018-12-310001126328us-gaap:EquityMethodInvestmentsMember2020-12-310001126328us-gaap:EquityMethodInvestmentsMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMember2020-01-012020-12-310001126328us-gaap:FairValueMeasurementsRecurringMember2019-01-012019-12-310001126328us-gaap:FairValueMeasurementsRecurringMember2018-01-012018-12-310001126328pfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2020-01-012020-12-310001126328pfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2019-01-012019-12-310001126328pfg:InvestmentAndUniversalLifeContractsMemberus-gaap:FairValueMeasurementsRecurringMember2018-01-012018-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueMeasurementsRecurringMember2020-01-012020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueMeasurementsRecurringMember2020-01-012020-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueMeasurementsRecurringMember2018-01-012018-12-310001126328us-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328us-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:TradingSecuritiesMember2020-01-012020-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-01-012020-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueMeasurementsRecurringMember2019-01-012019-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-01-012018-12-310001126328us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-01-012018-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberpfg:TradingSecuritiesMember2018-01-012018-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-01-012020-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-01-012020-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-01-012020-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2020-01-012020-12-310001126328us-gaap:OtherDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-01-012019-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-01-012019-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-01-012019-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-01-012019-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2019-01-012019-12-310001126328pfg:InvestmentsOtherMemberus-gaap:FairValueMeasurementsRecurringMember2019-01-012019-12-310001126328us-gaap:DebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-01-012018-12-310001126328us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-01-012018-12-310001126328us-gaap:CommercialMortgageBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-01-012018-12-310001126328us-gaap:CollateralizedDebtObligationsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:AvailableforsaleSecuritiesMember2018-01-012018-12-310001126328pfg:SeparateAccountAssetsMemberus-gaap:FairValueMeasurementsRecurringMember2018-01-012018-12-310001126328us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember2020-01-012020-12-310001126328us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember2019-01-012019-12-310001126328us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember2018-01-012018-12-310001126328pfg:EmployeeStockPurchasePlanMember2020-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2020-01-012020-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2020-01-012020-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2019-01-012019-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2019-01-012019-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2018-01-012018-12-310001126328srt:ParentCompanyMembersrt:ReportableLegalEntitiesMember2018-01-012018-12-310001126328pfg:SubsidiariesPrincipalLifeInsuranceCompanyMember2020-01-012020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328us-gaap:FairValueMeasurementsRecurringMember2020-12-310001126328us-gaap:FairValueInputsLevel3Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328us-gaap:FairValueMeasurementsRecurringMember2019-12-310001126328us-gaap:StockOptionMember2020-12-310001126328us-gaap:InterestRateSwapMember2020-12-310001126328us-gaap:ForeignExchangeForwardMember2020-12-310001126328us-gaap:CurrencySwapMember2020-12-310001126328us-gaap:CreditDefaultSwapMember2020-12-310001126328pfg:InterestRateOptionsMember2020-12-310001126328pfg:InterestRateForwardsMember2020-12-310001126328us-gaap:StockOptionMember2019-12-310001126328us-gaap:InterestRateSwapMember2019-12-310001126328us-gaap:ForeignExchangeOptionMember2019-12-310001126328us-gaap:ForeignExchangeForwardMember2019-12-31