Name:	pfg_ContractholderFunds
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	pfg_DepositContractsLiabilitiesAbstract
Namespace Prefix:	pfg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Carrying amount of liabilities as of the balance sheet date pertaining to amounts received by the insurer for investment-type insurance contracts not otherwise specified in the taxonomy.

No definition available.

Name:	pfg_DepositContractsLiabilitiesOther
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of the liability as of the balance sheet date pertaining to amounts received by the insurer for funding agreements.

No definition available.

Name:	pfg_FundingAgreements
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of the liability as of the balance sheet date pertaining to liabilities for individual annuities.

No definition available.

Name:	pfg_LiabilityForFuturePolicyBenefitsIndividualAnnuities
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount as of the balance sheet date pertaining to reserves for universal life and other reserves.

No definition available.

Name:	pfg_LiabilityForFuturePolicyBenefitsUniversalLifeAndOtherReserves
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Carrying amount of liabilities as of the balance sheet date pertaining to amounts received by the insurer or reinsurer from the insured (including a ceding company) under insurance or reinsurance contracts for which insurance risk is not transferred.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 98-7

-Paragraph 18

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 340

-SubTopic 30

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6387650&loc=d3e9420-108338

Name:	us-gaap_DepositContractsLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of the liability as of the balance sheet date pertaining to the guarantee given by the insurance entity to contract holders of a specified rate of return (a guaranteed yield) on their investments for a specified period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 7

-Section 03

-Paragraph 13, 14

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.14)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910