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Amount of revenue resulting from transactions with other operating segments of the same entity.

No definition available.

Name:	pfg_IntersegmentRevenue
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Data Type:	xbrli:monetaryItemType
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Operating revenues is a measure of revenue for the operating segments. It is derived by adjusting total revenues for net realized capital gains and losses (except periodic settlements and accruals on derivatives not designated as hedging instruments), including their impact on recognition of front-end fee revenues, certain market value adjustments to fee revenues and amortization of hedge accounting book value adjustments for certain discontinued hedges, and revenue from the exited group medical insurance business. Operating revenues also includes operating revenues from real estate properties that qualify for discontinued operations.

No definition available.

Name:	pfg_OperatingRevenues
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Data Type:	xbrli:monetaryItemType
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Aggregate revenue recognized during the period on a tax indemnification.

No definition available.

Name:	pfg_OtherIncomeOnTaxIndemnification
Namespace Prefix:	pfg_
Data Type:	xbrli:monetaryItemType
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Net realized capital gains (losses) net of recognition of deferred front-end fee revenues for sales charges on retirement products and services and certain market value adjustments to fee revenues. It excludes periodic settlements and accruals on derivatives not designated as hedging instruments.

No definition available.

Name:	pfg_SegmentReportingInformationNetRealizedCapitalGainsLosses
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Data Type:	xbrli:monetaryItemType
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688