Deferred Acquisition Costs (Schedule Of Deferred Acquisition Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 6,668.0	$ 5,103.0	$ 3,484.5
Costs deferred	3,736.1	3,747.3	3,094.0
Amortization	(2,830.6)	(2,182.3)	(1,475.5)
Ending balance	$ 7,573.5	$ 6,668.0	$ 5,103.0