Future Policy Benefits and Claims - Interest Accretion and Current Discount Rates (Details)	Mar. 31, 2023	Dec. 31, 2022
Retirement and Income Solutions \| Pension risk transfer
Future Policy Benefits and Claims
Interest accretion rate	4.40%	4.38%
Current discount rate	4.96%	5.31%
Retirement and Income Solutions \| Individual fixed income annuities
Future Policy Benefits and Claims
Interest accretion rate	4.21%	4.22%
Current discount rate	4.94%	5.30%
Principal Asset Management \| Principal International \| Latin America \| Individual fixed income annuities
Future Policy Benefits and Claims
Interest accretion rate	4.24%	4.24%
Current discount rate	2.50%	2.43%
Benefits and Protection \| Specialty Benefits \| Individual disability
Future Policy Benefits and Claims
Interest accretion rate	4.01%	4.03%
Current discount rate	5.01%	5.36%
Benefits and Protection \| Life Insurance \| Universal life
Future Policy Benefits and Claims
Interest accretion rate	4.73%	4.73%
Benefits and Protection \| Life Insurance \| Term life
Future Policy Benefits and Claims
Interest accretion rate	4.85%	4.89%
Current discount rate	4.83%	5.22%
Corporate \| Long-term care insurance
Future Policy Benefits and Claims
Interest accretion rate	6.16%	6.16%
Current discount rate	5.00%	5.34%

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.

+ Details

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

- Definition

Current weighted-average discount rate used to measure liability for future policy benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (b)(6)
-URI https://asc.fasb.org/extlink&oid=124506351&loc=d3e14931-158439

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 55
-Paragraph 29E
-URI https://asc.fasb.org/extlink&oid=126561865&loc=SL117819541-158441

+ Details

Name:	us-gaap_LiabilityForFuturePolicyBenefitCurrentWeightedAverageDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Original weighted-average discount rate at contract issue date used to measure liability for future policy benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 55
-Paragraph 29E
-URI https://asc.fasb.org/extlink&oid=126561865&loc=SL117819541-158441

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (b)(6)
-URI https://asc.fasb.org/extlink&oid=124506351&loc=d3e14931-158439

+ Details

Name:	us-gaap_LiabilityForFuturePolicyBenefitWeightedAverageInterestAccretionRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=pfg_SegmentRetirementAndIncomeSolutionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=pfg_PensionRiskTransferMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_FixedAnnuityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=pfg_SegmentPrincipalAssetManagementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsegmentsAxis=pfg_SubsegmentPrincipalInternationalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=srt_LatinAmericaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=pfg_SegmentBenefitsAndProtectionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsegmentsAxis=pfg_SubsegmentSpecialtyBenefitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=pfg_IndividualDisabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsegmentsAxis=pfg_SubsegmentLifeInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_UniversalLifeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_TermLifeInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=pfg_SegmentCorporateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=pfg_LongTermCareInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: