Legal Proceedings And Contingencies - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended								69 Months Ended
	Sep. 30, 2012 Year	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Other Noncurrent Liabilities	Dec. 31, 2011 Other Noncurrent Liabilities	Sep. 30, 2012 Other Noncurrent Assets	Dec. 31, 2011 Other Noncurrent Assets	Sep. 30, 2012 N.Y. Metropolitan Transportation Authority	Apr. 24, 2009 N.Y. Metropolitan Transportation Authority	Sep. 30, 2012 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	959,000,000	959,000,000	932,000,000	854,000,000	814,000,000
Environmental costs eligible for future recovery	832,000,000	832,000,000	808,000,000			741,000,000	706,000,000
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	2,300,000,000	2,300,000,000	3,900,000,000
Third-party guarantees outstanding	853,000,000	853,000,000	907,000,000
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										462,000,000
Revolving line of credit										$ 560,000,000