Segment Information (Financial Data By Reportable Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Operating revenue	$ 18,370.7	$ 17,618.7	$ 54,245.5	$ 52,545.7
Operating gain (loss)	1,191.3	1,001.0	3,532.9	3,582.0
Commercial and Specialty Business [Member]
Segment Reporting Information [Line Items]
Operating revenue	9,809.1	9,833.3	29,471.6	29,492.5
Operating gain (loss)	915.7	711.7	2,721.4	2,922.3
Government Business [Member]
Segment Reporting Information [Line Items]
Operating revenue	8,555.4	7,772.6	24,756.0	23,028.9
Operating gain (loss)	283.9	294.6	837.0	678.5
Other [Member]
Segment Reporting Information [Line Items]
Operating revenue	6.2	12.8	17.9	24.3
Operating gain (loss)	$ (8.3)	$ (5.3)	$ (25.5)	$ (18.8)