Revenue Recognition - Reconciliation of Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Reconciliation of Contract Balances
Notes and accounts receivable - trade (net of allowances)	$ 6,753		$ 6,753		$ 7,432
Notes and accounts receivable - trade, allowances	286		286		309
Contract assets	513		513		470
Deferred income (current)	11,223		11,223		11,165
Deferred income (noncurrent)	3,382		3,382		$ 3,445
Revenue recognized that was included in deferred income at the beginning of the period	$ 3,600	$ 3,800	$ 7,700	$ 8,000