Reinsurance - Cost of Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reinsurance
Cost of reinsurance asset	$ 3,275.5	$ 3,339.1
Cost of reinsurance liability	424.6	479.8
Cost of reinsurance amortization	$ 17.7	$ 19.3	$ 23.0

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