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

Describes, in the context of the estimate of credit derivatives purchased, the fair value for any purchased credit protection with identical underlying(s).

No definition available.

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

Discloses the notional amount of the credit derivatives sold (or each group of similar credit derivatives) as of the date of the statement of financial position.

No definition available.

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

Discloses the fair value of the credit derivatives sold (or each group of similar credit derivatives) as of the date of the statement of financial position.

No definition available.

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

Represents the weighted-average expected life in years for credit derivatives sold.

No definition available.

Name:	pfg_CreditDerivativesSoldWeightedAverageExpectedLife
Namespace Prefix:	pfg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the maximum potential amount of future payments (undiscounted) the seller could be required to make under the credit derivative or each group of similar credit derivatives before reduction for potential recoveries under recourse or collateralization provisions in the credit derivative.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4K

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5708775-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Credit Derivative

-URI http://asc.fasb.org/extlink&oid=6854095

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44DD

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.