Revenue Recognition (Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other current assets	$ 12,008	$ 10,757
Other Assets	20,974	18,444
Accounts payable and accrued liabilities	31,569	34,470
Advanced billings and customer deposits	5,081	4,213
Deferred income taxes	45,730	43,207
Other noncurrent liabilities	19,117	19,747
Retained Earnings	55,067	50,500
Accumulated other comprehensive income	7,386	7,017	$ 5,160	$ 4,961
Noncontrolling interest	1,156	$ 1,146
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other current assets	10,124
Other Assets	19,164
Accounts payable and accrued liabilities	31,748
Advanced billings and customer deposits	5,140
Deferred income taxes	44,787
Other noncurrent liabilities	18,990
Retained Earnings	52,250
Accumulated other comprehensive income	7,375
Noncontrolling interest	$ 1,115