Segment Information (Financial Data By Reportable Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Operating revenue	$ 18,230.0	$ 17,491.9	$ 35,874.8	$ 34,927.0
Operating gain (loss)	1,222.9	1,223.7	2,341.6	2,581.0
Commercial and Specialty Business [Member]
Segment Reporting Information [Line Items]
Operating revenue	9,965.0	9,799.8	19,662.5	19,659.2
Operating gain (loss)	919.6	948.5	1,805.7	2,210.6
Government Business [Member]
Segment Reporting Information [Line Items]
Operating revenue	8,259.3	7,686.9	16,200.6	15,256.3
Operating gain (loss)	313.5	281.3	553.1	383.9
Other [Member]
Segment Reporting Information [Line Items]
Operating revenue	5.7	5.2	11.7	11.5
Operating gain (loss)	$ (10.2)	$ (6.1)	$ (17.2)	$ (13.5)