Other Financial Data (Other Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Other Liabilities [Abstract]
Defined benefit plans	$ 1,512	$ 1,611
Postretirement health care benefit plan	49	49
Deferred revenue	113	139
Unrecognized tax benefits	50	54
Other	180	158
Other liabilities	$ 1,904	$ 2,011