Changes in Estimates (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
Changes in Estimates (Details) [Abstract]
Increase in Operating Income Due to Aggregate Net Changes in Contract Estimates	$ 23	$ 16	$ 38	$ 49
Cummulative operating income adjustment on CRS contract	$ 12		$ 12
Estimated profit margin on CRS contract minimum	5.50%		5.50%
Estimated profit margin on CRS contract maximum	6.25%		6.25%