Future Policy Benefits and Claims - Disaggregated Amounts Included in Future Policy Benefits and Claims (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Future Policy Benefits and Claims
Liability for future policy benefits	$ 35,747.6	$ 36,514.6
Additional liability for certain benefit features	5,444.0	5,326.5
Participating contracts	3,027.1	3,060.5
Short-duration contracts	1,287.0	1,283.4
Cost of reinsurance liability	409.8	424.6
Reinsurance recoverable liability	40.5	45.2
Other	140.3	171.7
Future policy benefits and claims per consolidated statements of financial position	46,096.3	46,826.5
Retirement and Income Solutions
Future Policy Benefits and Claims
Liability for future policy benefits	28,620.8	28,769.9
Retirement and Income Solutions | Pension risk transfer
Future Policy Benefits and Claims
Liability for future policy benefits	23,857.5	23,855.8
Retirement and Income Solutions | Individual fixed income annuities
Future Policy Benefits and Claims
Liability for future policy benefits	4,763.3	4,914.1
Principal Asset Management | Principal International | Latin America | Individual fixed income annuities
Future Policy Benefits and Claims
Liability for future policy benefits	4,015.2	4,593.7
Benefits and Protection
Future Policy Benefits and Claims
Liability for future policy benefits	2,947.1	2,984.3
Benefits and Protection | Specialty Benefits | Individual disability
Future Policy Benefits and Claims
Liability for future policy benefits	1,854.9	1,898.4
Benefits and Protection | Life Insurance | Term life
Future Policy Benefits and Claims
Liability for future policy benefits	1,092.2	1,085.9
Benefits and Protection | Life Insurance | Universal life
Future Policy Benefits and Claims
Additional liability for certain benefit features	5,444.0	5,326.5
Corporate | Long-term care insurance
Future Policy Benefits and Claims
Liability for future policy benefits	$ 164.5	$ 166.7