Revenues from Contracts with Customers - Disaggregation within Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues from Contracts with Customers - Disaggregation of Revenues
Total fees and other revenues	$ 4,177.7	$ 5,012.6	$ 4,511.1
Premiums and other considerations	5,339.7	4,841.5	6,037.4
Net investment income (loss)	3,830.4	4,406.1	3,890.6
Retirement and Income Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Premiums and other considerations	1,959.7	1,883.6	3,221.0
Net investment income (loss)	2,252.2	2,674.4	2,457.9
Principal Global Investors
Revenues from Contracts with Customers - Disaggregation of Revenues
Net investment income (loss)	13.1	3.9	5.6
Principal International
Revenues from Contracts with Customers - Disaggregation of Revenues
Premiums and other considerations	77.7	127.5	156.6
Net investment income (loss)	818.7	631.1	446.8
U.S. Insurance Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Premiums and other considerations	3,306.5	2,830.4	2,659.8
Net investment income (loss)	564.2	917.1	850.6
Corporate
Revenues from Contracts with Customers - Disaggregation of Revenues
Premiums and other considerations	(4.2)
Net investment income (loss)	182.2	179.6	129.7
Operating Segments
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	2,880.9	3,150.1	2,768.3
Total operating revenues	13,475.0	14,458.2	14,579.9
Operating Segments | Retirement and Income Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	551.4	590.1	599.8
Total operating revenues	5,975.2	6,510.0	7,503.5
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Fee
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	540.0	580.2	591.2
Fees and other revenues not within the scope of revenue recognition guidance	1,187.1	1,299.6	1,130.4
Total fees and other revenues	1,727.1	1,879.8	1,721.6
Premiums and other considerations		0.5	5.0
Net investment income (loss)	526.8	442.4	423.2
Total operating revenues	2,253.9	2,322.7	2,149.8
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Fee | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	537.0	576.7	589.2
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Fee | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	3.0	3.5	2.0
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Spread
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	11.4	9.9	8.6
Fees and other revenues not within the scope of revenue recognition guidance	2.9	7.9	9.5
Total fees and other revenues	14.3	17.8	18.1
Premiums and other considerations	1,959.7	1,883.1	3,216.0
Net investment income (loss)	1,747.3	2,286.4	2,119.6
Total operating revenues	3,721.3	4,187.3	5,353.7
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Spread | Deposit account fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	10.2	9.2	8.4
Operating Segments | Retirement and Income Solutions | Retirement and Income Solutions - Spread | Commission income
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	1.2	0.7	0.2
Operating Segments | Principal Global Investors
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	1,675.0	1,787.9	1,511.2
Fees and other revenues not within the scope of revenue recognition guidance	27.4	36.2	22.3
Total fees and other revenues	1,702.4	1,824.1	1,533.5
Net investment income (loss)	13.1	3.9	5.6
Total operating revenues	1,715.5	1,828.0	1,539.1
Operating Segments | Principal Global Investors | Management fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	1,434.6	1,514.1	1,298.4
Operating Segments | Principal Global Investors | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	240.4	273.8	212.8
Operating Segments | Principal International
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	426.3	492.7	439.2
Fees and other revenues not within the scope of revenue recognition guidance	4.5	4.1	5.6
Total fees and other revenues	430.8	496.8	444.8
Premiums and other considerations	77.7	127.5	156.6
Net investment income (loss)	967.4	727.5	495.4
Total operating revenues	1,475.9	1,351.8	1,096.8
Operating Segments | Principal International | Latin America
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	314.4	362.6	323.5
Operating Segments | Principal International | Asia
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	111.9	128.8	115.9
Operating Segments | Principal International | Principal International Corporate / Regional Office
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	2.0	2.6	0.9
Operating Segments | Principal International | Geographical Eliminations
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	(2.0)	(1.3)	(1.1)
Operating Segments | Principal International | Management fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	417.1	484.4	435.3
Operating Segments | Principal International | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	9.2	8.3	3.9
Operating Segments | U.S. Insurance Solutions
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	80.1	75.3	63.2
Total operating revenues	4,314.9	4,766.6	4,480.2
Operating Segments | U.S. Insurance Solutions | Specialty Benefits insurance
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	15.1	14.9	14.8
Fees and other revenues not within the scope of revenue recognition guidance	18.6	19.0	19.3
Total fees and other revenues	33.7	33.9	34.1
Premiums and other considerations	2,771.1	2,496.4	2,330.7
Net investment income (loss)	179.8	179.3	160.6
Total operating revenues	2,984.6	2,709.6	2,525.4
Operating Segments | U.S. Insurance Solutions | Specialty Benefits insurance | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	15.1	14.9	14.8
Operating Segments | U.S. Insurance Solutions | Individual Life insurance
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	65.1	60.6	48.6
Fees and other revenues not within the scope of revenue recognition guidance	333.6	859.2	849.8
Total fees and other revenues	398.7	919.8	898.4
Premiums and other considerations	535.9	334.0	329.1
Net investment income (loss)	396.3	803.4	727.5
Total operating revenues	1,330.9	2,057.2	1,955.0
Operating Segments | U.S. Insurance Solutions | Individual Life insurance | Administrative service fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	27.6	26.7	21.8
Operating Segments | U.S. Insurance Solutions | Individual Life insurance | Commission income
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	37.5	33.9	26.8
Operating Segments | Corporate
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	148.1	204.1	154.9
Fees and other revenues not within the scope of revenue recognition guidance	(318.3)	(360.0)	(303.9)
Total fees and other revenues	(170.2)	(155.9)	(149.0)
Premiums and other considerations	(4.2)
Net investment income (loss)	167.9	157.7	109.3
Total operating revenues	(6.5)	1.8	(39.7)
Operating Segments | Corporate | Other fee revenue
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	79.7	68.8	59.1
Operating Segments | Corporate | Commission income
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	366.2	388.9	316.6
Operating Segments | Corporate | Revenue by type - Eliminations
Revenues from Contracts with Customers - Disaggregation of Revenues
Total revenues from contracts with customers	$ (297.8)	$ (253.6)	$ (220.8)