Fair Value Of Assets And Liabilities - Fair Value Of Financial Instruments Held By Consolidated Investments (Details) - USD ($) $ in Millions	Mar. 31, 2021		Dec. 31, 2020	Mar. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 1,158.3		$ 1,408.4	$ 940.5
Restricted cash	208.0	[1]	129.2	$ 0.0
Foreign time deposits	29.3		29.9
Policyholder payables	(5,629.5)		(7,582.1)
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,158.3		1,408.4
Restricted cash	208.0		129.2
Equity investments	347.8		360.3
Foreign time deposits	29.3		29.9
Assets held for policyholders	5,629.5		7,582.1
Policyholder payables	(5,629.5)		(7,582.1)
Contingent consideration liability	$ (4.4)		$ (18.6)

[1] Restricted cash of $208.0 million and $129.2 million as of March 31, 2021 and December 31, 2020, respectively (March 31, 2020: zero) is recorded in Other assets on the Condensed Consolidated Balance Sheets.