Segment Information (Financial Data By Reportable Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 segment	Sep. 30, 2012
Segment Reporting Information [Line Items]
Reportable segments			3
Operating revenue from external customers	$ 17,733.0	$ 15,133.7	$ 52,876.5	$ 45,457.2
Operating gain (loss)	1,009.4	1,003.8	3,608.7	3,208.1
Commercial and Specialty Business [Member]
Segment Reporting Information [Line Items]
Operating revenue from external customers	9,789.1	9,751.2	29,358.7	29,391.7
Operating gain (loss)	688.2	852.3	2,869.9	2,863.2
Government Business [Member]
Segment Reporting Information [Line Items]
Operating revenue from external customers	7,931.1	5,374.1	23,493.5	16,039.2
Operating gain (loss)	326.5	169.0	757.6	381.8
Other [Member]
Segment Reporting Information [Line Items]
Operating revenue from external customers	12.8	8.4	24.3	26.3
Operating gain (loss)	$ (5.3)	$ (17.5)	$ (18.8)	$ (36.9)