Reinsurance - Cost of Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Reinsurance
Cost of reinsurance asset	$ 3,255.0		$ 3,275.5
Cost of reinsurance liability	409.8		$ 424.6
Cost of reinsurance amortization	$ 5.5	$ 17.8

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