Reinsurance - Cost of Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Reinsurance
Cost of reinsurance asset	$ 3,315.0		$ 3,339.1
Cost of reinsurance liability	184.5		$ 191.1
Cost of reinsurance amortization	$ 17.8	$ (5.5)

The reinsurance liability related to the amount of expected net reinsurance costs or profits to be spread over the expected term of the contracts.

No definition available.

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