Segment Information (Reconciliation Of Reportable Segments Operating Gain To Income Before Income Tax Expense Included In The Consolidated Statements Of Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting [Abstract]
Reportable segments operating gain	$ 982.0	$ 1,078.1	$ 3,794.4	$ 4,148.7
Net investment income	220.2	200.9	627.6	566.9
Net realized gains (losses) on financial instruments	114.7	88.8	138.2	(23.8)
Other-than-temporary impairment losses recognized in income	(5.6)	(11.0)	(20.9)	(103.6)
Interest expense	(150.5)	(172.9)	(575.4)	(545.7)
Amortization of other intangible assets	(41.9)	(47.4)	(124.3)	(145.7)
Income before income tax expense	$ 1,118.9	$ 1,136.5	$ 3,839.6	$ 3,896.8