Name:	pfg_CashAndCashEquivalentsMaximumMaturityPeriod
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Represents the minimum number of years for the maturity date debt when issued for it to be included in long-term debt.

No definition available.

Name:	pfg_LongTermDebtMinimumMaturityPeriod
Namespace Prefix:	pfg_
Data Type:	xbrli:durationItemType
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Period Type:	duration

This percent places participating policies in the numerator and life insurance premiums in the denominator. Participating insurance contracts allow policyholders to share in the experience of the entity, primarily through policy dividends.

No definition available.

Name:	pfg_ParticipatingPoliciesAsPercentageOfLifeInsurancePremiums
Namespace Prefix:	pfg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

This percent places participating policies in the numerator and total number of life insurance policies in force in the denominator. Participating insurance contracts allow policyholders to share in the experience of the entity, primarily through policy dividends.

No definition available.

Name:	pfg_ParticipatingPoliciesAsPercentageOfNumberOfLifeInsurancePoliciesInForce
Namespace Prefix:	pfg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Amount of net ceded reinsurance recoverables related to claims that have been received.

No definition available.

Name:	pfg_ReinsuranceRecoverablesClaimsReceived
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This item represents the value of a separate account that primarily includes shares of Principal Financial Group, Inc. stock that were allocated and issued to eligible participants of qualified employee benefit plans administered as part of the policy credits issued under the 2001 demutualization.

No definition available.

Name:	pfg_SeparateAccountWithSharesOfPrincipalFinancialGroupStock
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The known and estimated amount recoverable as of the balance sheet date from the largest reinsurer in individual life business for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance.

No definition available.

Name:	pfg_ThirdPartyReinsurerEntityExposureAmountLimitedToReinsuranceRecoverable
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount at risk of not being collected pertaining to a reinsurer with the largest exposure in individual life insurance business with respect to disclosure of a concentration of credit risk.

No definition available.

Name:	pfg_ThirdPartyReinsurerEntityMaximumExposureAmountOfLifeInsuranceInForce
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The largest exposure to a single third-party reinsurer in individual life insurance business as a percentage of total net individual life insurance in force.

No definition available.

Name:	pfg_ThirdPartyReinsurerEntityMaximumExposureAsPercentageOfLifeInsuranceInForce
Namespace Prefix:	pfg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Amount of earned premiums assumed from other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-17)
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

No definition available.

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

Amount of earned premiums ceded to other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Subparagraph (SX 210.7-04.1)
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Topic 944
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Name:	us-gaap_DirectPremiumsEarned
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

No definition available.

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

No definition available.

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

No definition available.

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This percent places participating policies in the numerator and insurance contracts in force in the denominator. Participating insurance contracts allow policyholders to share in the experience of the entity, primarily through policy dividends.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SX 210.7-03.14(b)(1))
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Name:	us-gaap_ParticipatingPoliciesAsPercentageOfGrossInsuranceInForce
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Amount, before effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred.

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

Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred.

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

No definition available.

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

Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(c))
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-17)
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Name:	us-gaap_PremiumsEarnedNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Carrying amount as of the balance sheet date of investments in land and buildings held for sale, excluding real estate considered to be inventory of the entity.

Name:	us-gaap_RealEstateHeldforsale
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

No definition available.

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

Amount of policy benefits and costs incurred for policies assumed.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387

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

Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

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

No definition available.

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

No definition available.