Legal Proceedings And Contingencies - Additional Information (Detail) (USD $)	3 Months Ended								75 Months Ended
	Mar. 31, 2013 Y	Dec. 31, 2012	Mar. 31, 2013 Other Noncurrent Liabilities	Dec. 31, 2012 Other Noncurrent Liabilities	Mar. 31, 2013 Other Noncurrent Assets	Dec. 31, 2012 Other Noncurrent Assets	Mar. 31, 2013 N.Y. Metropolitan Transportation Authority	Apr. 24, 2009 N.Y. Metropolitan Transportation Authority	Mar. 31, 2013 United Launch Alliance
Site Contingency [Line Items]
Contract value								$ 323,000,000
Contract payments received to date							241,000,000
Liabilities recorded relative to environmental matters	986,000,000	950,000,000	883,000,000	844,000,000
Environmental costs eligible for future recovery	853,000,000	821,000,000			762,000,000	730,000,000
Time period environmental costs and recovery of environmental costs are projected over, years	20
Percentage of expenditures that are reimbursed for certain remediation activities	50.00%
Outstanding letters of credit, surety bonds, and third-party guarantees	2,400,000,000	2,200,000,000
Third-party guarantees outstanding	817,000,000	816,000,000
Percentage of total guarantees that relate to guarantees of contractual performance of joint ventures	85.00%	85.00%
Percentage of ownership interest in affiliated entity									50.00%
Dividends that are subject to contingency									527,000,000
Revolving line of credit									$ 560,000,000