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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting [Abstract]
Reportable segments operating revenues									$ 78,404.8	$ 73,021.7	$ 70,191.4
Net investment income									677.6	724.4	659.1
Net realized gains on investments									157.5	177.0	271.9
Other-than-temporary impairment losses recognized in income									(83.4)	(49.0)	(98.9)
Total revenues	$ 20,187.9	$ 19,901.6	$ 20,015.5	$ 19,051.5	$ 18,984.3	$ 18,557.0	$ 18,473.4	$ 17,859.4	$ 79,156.5	$ 73,874.1	$ 71,023.5