Summary of Significant Accounting Policies (Details 4) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in Accounting Estimate [Line Items]
Operating Income (Loss)	$ 831	$ 826	$ 797	$ 739	$ 689	$ 794	$ 813	$ 780	$ 3,193	$ 3,076	$ 3,196
Net earnings	$ 525	$ 602	$ 517	$ 556	$ 459	$ 516	$ 531	$ 484	$ 2,200	$ 1,990	$ 2,069
Diluted earnings per share	$ 2.96	$ 3.35	$ 2.85	$ 3.03	$ 2.49	$ 2.75	$ 2.74	$ 2.41	$ 12.19	$ 10.39	$ 9.75
Contracts Accounted for under Percentage of Completion [Member]
Change in Accounting Estimate [Line Items]
Operating Income (Loss)									$ 494	$ 580	$ 664
Net earnings									$ 321	$ 377	$ 432
Diluted earnings per share									$ 1.78	$ 1.97	$ 2.04