| Cover | Apr. 27, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Apr. 27, 2021 |
| Entity File Number | 1-16725 |
| Entity Registrant Name | PRINCIPAL FINANCIAL GROUP INC |
| Entity Central Index Key | 0001126328 |
| Entity Tax Identification Number | 42-1520346 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 711 High Street |
| Entity Address, City or Town | Des Moines |
| Entity Address, State or Province | IA |
| Entity Address, Postal Zip Code | 50392 |
| City Area Code | 515 |
| Local Phone Number | 247-5111 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | PFG |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
