Revenues from Contracts with Customers - Disaggregation within Segments (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	$ 995.3	$ 1,219.2
Premiums and other considerations	1,448.6	887.4
Net investment income (loss)	986.7	1,125.5
Operating Segments
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	685.1	750.2
Total operating revenues	3,439.6	3,268.5
Operating Segments | Benefits and Protection
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	20.6	19.4
Total operating revenues	1,103.4	1,243.3
Operating Segments | Benefits and Protection | Specialty Benefits
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	3.9	4.0
Fees and other revenues not within the scope of revenue recognition guidance	4.6	4.7
Total fees and other revenues	8.5	8.7
Premiums and other considerations	733.6	665.6
Net investment income (loss)	40.1	43.4
Total operating revenues	782.2	717.7
Operating Segments | Benefits and Protection | Specialty Benefits | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	3.9	4.0
Operating Segments | Benefits and Protection | Life Insurance
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	16.7	15.4
Fees and other revenues not within the scope of revenue recognition guidance	77.3	228.3
Total fees and other revenues	94.0	243.7
Premiums and other considerations	130.8	88.8
Net investment income (loss)	96.6	193.2
Total operating revenues	321.4	525.7
Operating Segments | Benefits and Protection | Life Insurance | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	7.2	6.8
Operating Segments | Benefits and Protection | Life Insurance | Commission income
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	9.5	8.6
Operating Segments | Principal Asset Management
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	489.2	533.4
Total operating revenues	692.5	755.9
Operating Segments | Principal Asset Management | Principal Global Investors
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	381.3	429.6
Fees and other revenues not within the scope of revenue recognition guidance	4.6	5.3
Total fees and other revenues	385.9	434.9
Net investment income (loss)	6.8	0.4
Total operating revenues	392.7	435.3
Operating Segments | Principal Asset Management | Principal Global Investors | Management fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	339.7	379.0
Operating Segments | Principal Asset Management | Principal Global Investors | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	41.6	50.6
Operating Segments | Principal Asset Management | Principal International
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	113.2	110.4
Fees and other revenues not within the scope of revenue recognition guidance	1.4	1.2
Total fees and other revenues	114.6	111.6
Premiums and other considerations	6.4	10.3
Net investment income (loss)	184.1	205.3
Total operating revenues	305.1	327.2
Operating Segments | Principal Asset Management | Principal International | Latin America
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	85.9	82.1
Operating Segments | Principal Asset Management | Principal International | Asia
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	27.5	28.5
Operating Segments | Principal Asset Management | Principal International | Geographical Eliminations
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	(0.2)	(0.2)
Operating Segments | Principal Asset Management | Principal International | Management fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	110.9	107.7
Operating Segments | Principal Asset Management | Principal International | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	2.3	2.7
Operating Segments | Retirement and Income Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	130.2	144.4
Fees and other revenues not within the scope of revenue recognition guidance	278.3	299.4
Total fees and other revenues	408.5	443.8
Premiums and other considerations	582.7	123.3
Net investment income (loss)	624.9	695.9
Total operating revenues	1,616.1	1,263.0
Operating Segments | Retirement and Income Solutions | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	126.5	141.5
Operating Segments | Retirement and Income Solutions | Deposit account fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	2.9	2.5
Operating Segments | Retirement and Income Solutions | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	0.4	0.2
Operating Segments | Retirement and Income Solutions | Commission income
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	0.4	0.2
Operating Segments | Corporate
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	45.1	53.0
Fees and other revenues not within the scope of revenue recognition guidance	(75.6)	(89.7)
Total fees and other revenues	(30.5)	(36.7)
Premiums and other considerations	(1.3)	(0.5)
Net investment income (loss)	59.4	43.5
Total operating revenues	27.6	6.3
Operating Segments | Corporate | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	20.5	19.8
Operating Segments | Corporate | Commission income
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	87.9	97.2
Operating Segments | Corporate | Revenue by type - Eliminations
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	$ (63.3)	$ (64.0)