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Employee and Agent Benefits - Plan Information (Details)	12 Months Ended
	Dec. 31, 2021
Pension benefits
Defined Benefit Plan Disclosures
Period of employment used to calculate average annual compensation for the final average pay benefit	5 years

X

- Definition

The final average pay benefit is based on the years of service and generally the employee's or agent's average annual compensation during the most recent years of employment for this time period.

+ References

No definition available.

+ Details

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

X

- Definition

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.

+ References

No definition available.

+ Details

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

X

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: