Segment Information (Reconciliation Of Revenue From Reportable Segments To The Consolidated Statements Of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Reportable segments operating revenues									$ 84,194.0	$ 78,404.8	$ 73,021.7
Net investment income									779.5	677.6	724.4
Net realized gains on financial instruments									4.9	157.5	177.0
Other-than-temporary impairment losses recognized in income									(115.4)	(83.4)	(49.0)
Total revenues	$ 21,714.4	$ 21,403.9	$ 21,456.2	$ 20,288.5	$ 20,187.9	$ 19,901.6	$ 20,015.5	$ 19,051.5	$ 84,863.0	$ 79,156.5	$ 73,874.1