Revenues from Contracts with Customers - Disaggregation by Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenues from Contracts with Customers - Disaggregation of Revenues
Total fees and other revenues per consolidated statements of operations	$ 995.3	$ 1,219.2
Operating Segments
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	685.1	750.2
Operating Segments | Retirement and Income Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	130.2	144.4
Adjustments for fees and other revenues not within the scope of revenue recognition guidance	278.3	299.4
Total fees and other revenues per consolidated statements of operations	408.5	443.8
Operating Segments | Principal Asset Management
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	489.2	533.4
Operating Segments | Benefits and Protection
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	20.6	19.4
Operating Segments | Corporate
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	45.1	53.0
Adjustments for fees and other revenues not within the scope of revenue recognition guidance	(75.6)	(89.7)
Total fees and other revenues per consolidated statements of operations	(30.5)	(36.7)
Operating Segments | Principal Global Investors | Principal Asset Management
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	381.3	429.6
Adjustments for fees and other revenues not within the scope of revenue recognition guidance	4.6	5.3
Total fees and other revenues per consolidated statements of operations	385.9	434.9
Operating Segments | Principal International | Principal Asset Management
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	113.2	110.4
Adjustments for fees and other revenues not within the scope of revenue recognition guidance	1.4	1.2
Total fees and other revenues per consolidated statements of operations	114.6	111.6
Operating Segments | Specialty Benefits | Benefits and Protection
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	3.9	4.0
Adjustments for fees and other revenues not within the scope of revenue recognition guidance	4.6	4.7
Total fees and other revenues per consolidated statements of operations	8.5	8.7
Operating Segments | Life Insurance | Benefits and Protection
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	16.7	15.4
Adjustments for fees and other revenues not within the scope of revenue recognition guidance	77.3	228.3
Total fees and other revenues per consolidated statements of operations	94.0	243.7
Operating Segments | Eliminations | Principal Asset Management
Revenues from Contracts with Customers - Disaggregation of Revenues
Total segment revenue from contracts with customers	(5.3)	(6.6)
Reconciling Items
Revenues from Contracts with Customers - Disaggregation of Revenues
Adjustments for fees and other revenues not within the scope of revenue recognition guidance	290.4	449.0
Pre-tax other adjustments	$ 19.8	$ 20.0