Revenue Recognition (Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other current assets	$ 16,278	$ 10,757
Other Assets	25,490	18,444
Accounts payable and accrued liabilities	39,375	34,470
Advanced billings and customer deposits	6,045	4,213
Deferred income taxes	60,495	43,207
Other noncurrent liabilities	26,490	19,747
Retained Earnings	57,624	50,500
Accumulated other comprehensive income	5,383	7,017	$ 5,580	$ 4,961
Noncontrolling interest	1,123	$ 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	13,750
Other Assets	23,050
Accounts payable and accrued liabilities	39,554
Advanced billings and customer deposits	6,109
Deferred income taxes	59,264
Other noncurrent liabilities	26,252
Retained Earnings	53,929
Accumulated other comprehensive income	5,385
Noncontrolling interest	$ 1,071