Goodwill and Other Intangible Assets - Changes in Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Changes in Goodwill
Beginning balance, Goodwill	$ 1,693.8	$ 1,100.0
Goodwill from acquisitions		623.9
Foreign currency, Goodwill	17.2	(30.1)
Ending balance, Goodwill	1,711.0	1,693.8
Retirement and Income Solutions
Changes in Goodwill
Beginning balance, Goodwill	675.9	57.4
Goodwill from acquisitions		618.5
Ending balance, Goodwill	675.9	675.9
Principal Global Investors
Changes in Goodwill
Beginning balance, Goodwill	317.5	307.3
Goodwill from acquisitions		6.5
Foreign currency, Goodwill	3.4	1.5
Other, Goodwill		2.2
Ending balance, Goodwill	320.9	317.5
Principal International
Changes in Goodwill
Beginning balance, Goodwill	642.8	676.6
Foreign currency, Goodwill	13.8	(31.6)
Other, Goodwill		(2.2)
Ending balance, Goodwill	656.6	642.8
U.S. Insurance Solutions
Changes in Goodwill
Beginning balance, Goodwill	56.6	56.6
Ending balance, Goodwill	56.6	56.6
Corporate
Changes in Goodwill
Beginning balance, Goodwill	1.0	2.1
Goodwill from acquisitions		(1.1)
Ending balance, Goodwill	$ 1.0	$ 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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-Publisher FASB
-Name Accounting Standards Codification
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Amount of increase (decrease), classified as other, of an asset representing the future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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