Segment Information (Reconciliation Of Reportable Segments Operating Revenues To Total Revenues Reported In The Consolidated Statements Of Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Segment Information [Abstract]
Reportable segments operating revenues	$ 15,150.2	$ 14,654.8
Net investment income	169.0	184.8
Net realized gains on investments	106.9	57.1
Other-than-temporary impairment losses recognized in income	(10.9)	(2.4)
Total revenues	$ 15,415.2	$ 14,894.3