Investments - Mortgage Loan Credit Monitoring (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2024	Dec. 31, 2023
Vintage year, Direct financing leases
2024	$ 44.9
2023	2.9	$ 46.1
2022	131.9	145.5
2021	45.6	48.8
2020	98.7	111.6
2019		12.9
Prior		285.2
Prior	271.9
Direct financing leases, Total amortized cost	595.9	650.1
Reinsurance recoverable and deposit receivable	19,737.9	20,614.9
Accrued interest receivable on direct financing leases	1.3	1.2
Mortgage and other loans
Accrued interest receivable	641.8	619.2
A- and above
Vintage year, Direct financing leases
2023	1.0	1.1
2022	41.2	122.0
2021	11.5	12.4
2020	35.6	56.7
2019		1.3
Prior		207.3
Prior	192.3
Direct financing leases, Total amortized cost	281.6	400.8
BBB+ thru BBB-
Vintage year, Direct financing leases
2024	5.0
2023	1.9	2.8
2022	90.1	23.5
2021	19.6	20.8
2020	55.6	46.9
2019		11.6
Prior		76.3
Prior	70.7
Direct financing leases, Total amortized cost	242.9	181.9
BB+ thru BB-
Vintage year, Direct financing leases
2024	39.9
2023		42.2
2022	0.6
2021	7.2	15.6
2020	3.6	8.0
Prior		1.6
Prior	8.9
Direct financing leases, Total amortized cost	60.2	67.4
B+ and below
Vintage year, Direct financing leases
2021	7.3
2020	3.9
Direct financing leases, Total amortized cost	11.2
Commercial mortgage loans
Vintage year, Mortgage loans
2024	654.8
2023	1,246.6	1,057.7
2022	1,721.9	1,775.3
2021	2,594.6	2,755.5
2020	1,770.1	1,802.0
2019		2,410.3
Prior	8,867.7
Prior		6,781.0
Mortgage loans, Total amortized cost	16,855.7	16,581.8
Mortgage and other loans
Accrued interest receivable	64.9	58.3
Commercial mortgage loans \| A- and above
Vintage year, Mortgage loans
2024	552.2
2023	813.2	664.8
2022	1,277.8	1,277.1
2021	2,269.5	2,364.0
2020	1,556.0	1,587.3
2019		1,954.4
Prior	7,146.5
Prior		5,576.6
Mortgage loans, Total amortized cost	13,615.2	13,424.2
Commercial mortgage loans \| BBB+ thru BBB-
Vintage year, Mortgage loans
2024	85.9
2023	306.8	282.4
2022	292.6	356.0
2021	265.5	374.8
2020	171.2	212.0
2019		337.3
Prior	1,109.5
Prior		911.7
Mortgage loans, Total amortized cost	2,231.5	2,474.2
Commercial mortgage loans \| BB+ thru BB-
Vintage year, Mortgage loans
2024	16.7
2023	126.6	110.5
2022	151.5	142.2
2021	59.6	16.7
2020	40.3	2.7
2019		35.2
Prior	239.3
Prior		234.2
Mortgage loans, Total amortized cost	634.0	541.5
Commercial mortgage loans \| B+ and below
Vintage year, Mortgage loans
2020	2.6
2019		83.4
Prior	372.4
Prior		58.5
Mortgage loans, Total amortized cost	375.0	141.9
Residential mortgage loans
Vintage year, Mortgage loans
2024	101.4
2023	445.9	503.4
2022	1,024.9	1,068.3
2021	1,295.6	1,346.7
2020	211.6	229.7
2019		122.8
Prior	492.4
Prior		425.6
Mortgage loans, Total amortized cost	3,571.8	3,696.5
Mortgage and other loans
Accrued interest receivable	11.2	11.4
Residential mortgage loans \| Performing
Vintage year, Mortgage loans
2024	101.3
2023	443.0	502.3
2022	1,017.7	1,064.3
2021	1,289.9	1,341.8
2020	208.8	228.4
2019		120.8
Prior	485.9
Prior		421.0
Mortgage loans, Total amortized cost	3,546.6	3,678.6
Residential mortgage loans \| Non-performing
Vintage year, Mortgage loans
2024	0.1
2023	2.9	1.1
2022	7.2	4.0
2021	5.7	4.9
2020	2.8	1.3
2019		2.0
Prior	6.5
Prior		4.6
Mortgage loans, Total amortized cost	$ 25.2	17.9
Mortgage and other loans
Mortgage loans, delinquent to be considered non-performing (in days)	90 days
Other loans
Vintage year, Mortgage loans
2024	$ 84.6
2023	98.8	168.5
Prior	0.1
Prior		0.1
Mortgage loans, Total amortized cost	183.5	168.6
Mortgage and other loans
Accrued interest receivable	1.5	1.6
Other loans \| Performing
Vintage year, Mortgage loans
2024	84.5
2023	98.8	168.5
Mortgage loans, Total amortized cost	183.3	168.5
Other loans \| Non-performing
Vintage year, Mortgage loans
2024	0.1
Prior	0.1
Prior		0.1
Mortgage loans, Total amortized cost	$ 0.2	$ 0.1

The numbers of days for which a mortgage loan has been delinquent such that it is considered non-performing.

No definition available.

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

- Definition

Carrying amount as of the balance sheet date of interest earned but not received on direct financing lease. Also called accrued interest or accrued interest receivable.

+ References

No definition available.

+ Details

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

- Definition

Amount of net investment in direct financing lease originated five years prior to current fiscal year.

+ References

No definition available.

+ Details

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

- Definition

Amount of net investment in direct financing lease originated six or more years prior to current fiscal year.

+ References

No definition available.

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable originated five or more years prior to current fiscal year. Excludes net investment in lease.

+ References

No definition available.

+ Details

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

- Definition

Amortized cost excluding accrued interest of financing receivable originated five years prior to current fiscal year. Excludes net investment in lease.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount excluding accrued interest, before allowance for credit loss, of net investment in direct financing lease.

+ References

+ Details

Name:	us-gaap_DirectFinancingLeaseNetInvestmentInLeaseExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of net investment in direct financing lease originated more than five years prior to current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

+ Details

Name:	us-gaap_DirectFinancingLeaseNetInvestmentInLeaseOriginatedFiveOrMoreYearsBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of net investment in direct financing lease originated four years prior to current fiscal year.

+ References

+ Details

Name:	us-gaap_DirectFinancingLeaseNetInvestmentInLeaseOriginatedFourYearsBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of net investment in direct financing lease originated in current fiscal year.

+ References

+ Details

Name:	us-gaap_DirectFinancingLeaseNetInvestmentInLeaseOriginatedInCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of net investment in direct financing lease originated in fiscal year prior to current fiscal year.

+ References

+ Details

Name:	us-gaap_DirectFinancingLeaseNetInvestmentInLeaseOriginatedInFiscalYearBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of net investment in direct financing lease originated three years prior to current fiscal year.

+ References

+ Details

Name:	us-gaap_DirectFinancingLeaseNetInvestmentInLeaseOriginatedThreeYearsBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of net investment in direct financing lease originated two years prior to current fiscal year.

+ References

+ Details

Name:	us-gaap_DirectFinancingLeaseNetInvestmentInLeaseOriginatedTwoYearsBeforeLatestFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated in current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477802/946-310-45-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(a)(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_InterestReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477409/944-310-45-5

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-14

+ Details

Name:	us-gaap_ReinsuranceRecoverablesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	srt_CreditRatingStandardPoorsAxis=pfg_StandardPoorsAMinusAndAboveRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingStandardPoorsAxis=pfg_StandardPoorsBBBPlusThruBBBMinusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingStandardPoorsAxis=pfg_StandardPoorsBBPlusThruBBMinusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingStandardPoorsAxis=pfg_StandardPoorsBPlusAndBelowRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=pfg_PerformingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=pfg_NonperformingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: