Other Financial Data - Accrued Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Accrued Liabilities [Abstract]
Deferred revenue	$ 469	$ 439
Compensation	232	250
Billings in excess of costs and earnings	408	434
Tax liabilities	168	111
Dividend payable	76	77
Trade liabilities	154	180
Other	536	620
Accrued liabilities	$ 2,043	$ 2,111