XML 165 R130.htm IDEA: XBRL DOCUMENT v2.4.1.9
Stock-Based Compensation Plans (Details 3) (USD $)
In Millions, except Per Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Performance Share Awards      
Change in nonvested units outstanding      
Awards or units outstanding at beginning of period (in shares) 1.0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Awards or units granted (in shares) 0.3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
0.3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
0.4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Awards or units vested (in shares) 0.3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Awards or units outstanding at end of period (in shares) 1.0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
1.0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
 
Awards or units outstanding at beginning of period weighted-average grant-date fair value (in dollars per share) $ 30.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Awards or units granted weighted-average grant-date fair value (in dollars per share) $ 44.88us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 30.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 27.46us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Awards or units vested weighted-average grant-date fair value (in dollars per share) $ 34.26us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Awards or units outstanding at end of period weighted-average grant-date fair value (in dollars per share) $ 33.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
$ 30.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
 
Other award and unit disclosures      
Lower limit multiple of initial target awards (as a percent) 0.00%pfg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsLowerMultipleOfInitialTargetBasedOnPerformance
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Upper limit multiple of initial target awards (as a percent) 150.00%pfg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsUpperLimitMultipleOfInitialTargetBasedOnPerformance
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Unrecognized compensation costs $ 4.0us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Weighted-average service period over which unrecognized compensation costs will be recognized 1 year 7 months 6 days    
Tax benefits realized for the tax deductions from awards or units paid out 4.0pfg_TaxBenefitsRealizedFromAwardsOrUnitsPaidOut
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
4.7pfg_TaxBenefitsRealizedFromAwardsOrUnitsPaidOut
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
4.7pfg_TaxBenefitsRealizedFromAwardsOrUnitsPaidOut
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Intrinsic value from awards or units vested 11.4pfg_IntrinsicValueFromAwardsOrUnitsVested
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
10.9pfg_IntrinsicValueFromAwardsOrUnitsVested
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
13.0pfg_IntrinsicValueFromAwardsOrUnitsVested
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Performance period for goals 3 years    
Restricted Stock Units      
Change in nonvested units outstanding      
Awards or units outstanding at beginning of period (in shares) 3.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
   
Awards or units granted (in shares) 0.9us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
1.3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
1.2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Awards or units vested (in shares) 0.8us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
   
Awards or units canceled (in shares) 0.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
   
Awards or units outstanding at end of period (in shares) 3.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
3.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Awards or units outstanding at beginning of period weighted-average grant-date fair value (in dollars per share) $ 30.46us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
   
Awards or units granted weighted-average grant-date fair value (in dollars per share) $ 45.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 31.02us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 27.33us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Awards or units vested weighted-average grant-date fair value (in dollars per share) $ 33.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
   
Awards or units canceled weighted-average grant-date fair value (in dollars per share) $ 33.27us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
   
Awards or units outstanding at end of period weighted-average grant-date fair value (in dollars per share) $ 33.87us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 30.46us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Other award and unit disclosures      
Unrecognized compensation costs 40.4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
   
Weighted-average service period over which unrecognized compensation costs will be recognized 1 year 8 months 12 days    
Tax benefits realized for the tax deductions from awards or units paid out 12.8pfg_TaxBenefitsRealizedFromAwardsOrUnitsPaidOut
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
11.5pfg_TaxBenefitsRealizedFromAwardsOrUnitsPaidOut
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
11.1pfg_TaxBenefitsRealizedFromAwardsOrUnitsPaidOut
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Intrinsic value from awards or units vested $ 38.5pfg_IntrinsicValueFromAwardsOrUnitsVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 37.7pfg_IntrinsicValueFromAwardsOrUnitsVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 31.9pfg_IntrinsicValueFromAwardsOrUnitsVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
2014 Stock Incentive Plan, Amended and Restated 2010 Stock Incentive Plan and Stock Incentive Plan | Restricted Stock Units      
Other award and unit disclosures      
Vesting period 3 years    
2014 Directors Stock Plan and 2005 Directors Stock Plan | Restricted Stock Units      
Other award and unit disclosures      
Vesting period 1 year