Segment Information - Reconciliation of Segment Assets to Consolidated (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Segment Information: Assets
Total assets	$ 282,580.6	$ 304,657.2
Retirement and Income Solutions
Segment Information: Assets
Total assets	201,000.7	221,993.8
Principal Global Investors
Segment Information: Assets
Total assets	2,239.1	2,445.1
Principal International
Segment Information: Assets
Total assets	37,535.1	42,812.4
U.S. Insurance Solutions
Segment Information: Assets
Total assets	39,969.5	33,222.6
Corporate
Segment Information: Assets
Total assets	$ 1,836.2	$ 4,183.3