Goodwill and Other Intangible Assets - Changes in Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Changes in Goodwill
Beginning balance, Goodwill	$ 1,627.6	$ 1,711.0
Goodwill disposed		(2.3)
Goodwill impairment	(27.1)	(1.0)
Foreign currency, Goodwill	(2.3)	(80.1)
Ending balance, Goodwill	1,598.2	1,627.6
Retirement and Income Solutions
Changes in Goodwill
Beginning balance, Goodwill	675.9	675.9
Ending balance, Goodwill	675.9	675.9
Principal Global Investors
Changes in Goodwill
Beginning balance, Goodwill	318.4	320.9
Foreign currency, Goodwill	(7.4)	(2.5)
Ending balance, Goodwill	311.0	318.4
Principal International
Changes in Goodwill
Beginning balance, Goodwill	576.7	656.6
Goodwill disposed		(2.3)
Foreign currency, Goodwill	5.1	(77.6)
Ending balance, Goodwill	581.8	576.7
U.S. Insurance Solutions
Changes in Goodwill
Beginning balance, Goodwill	56.6	56.6
Goodwill impairment	(27.1)
Ending balance, Goodwill	$ 29.5	56.6
Corporate
Changes in Goodwill
Beginning balance, Goodwill		1.0
Goodwill impairment		$ (1.0)

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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