Revenue Recognition - Transition Disclosures, Statement of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 6,777	$ 6,807
Adjustments to reconcile net income to cash provided by operating activities
Changes in operating assets and liabilities, net of acquisitions/divestitures	631	312
Net cash provided by operating activities	11,128	$ 10,991
Accounting Standards Update 2014-09, Revenue from Contracts with Customers | Adjustments to convert to prior GAAP
Cash flows from operating activities:
Net income	17
Adjustments to reconcile net income to cash provided by operating activities
Changes in operating assets and liabilities, net of acquisitions/divestitures	(17)
Accounting Standards Update 2014-09, Revenue from Contracts with Customers | Adjusted amounts under prior GAAP
Cash flows from operating activities:
Net income	6,794
Adjustments to reconcile net income to cash provided by operating activities
Changes in operating assets and liabilities, net of acquisitions/divestitures	614
Net cash provided by operating activities	$ 11,128