Fair Value Of Assets And Liabilities (Fair Value Of Financial Instruments Held By Consolidated Investments) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		$ 1,408.4	$ 1,049.0	$ 1,147.7
Restricted cash	[1]	129.2	0.0	$ 0.0
Foreign time deposits		29.9	32.0
Assets held for policyholders		7,582.1	10,835.6
Policyholder payables		(7,582.1)	(10,835.6)
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		1,408.4	1,049.0
Restricted cash		129.2	0.0
Equity investments		360.3	432.5
Foreign time deposits		29.9	32.0
Assets held for policyholders		7,582.1	10,835.6
Policyholder payables		(7,582.1)	(10,835.6)
Contingent consideration liability		$ (18.6)	$ (60.2)

[1] Restricted cash of $129.2 million as of December 31, 2020 is recorded in Other assets on the Consolidated Balance Sheet