Revenue Recognition - Reconciliation of Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Reconciliation of Contract Balances
Notes and accounts receivable - trade (net of allowances of $354 in 2020 and $299 in 2019)	$ 6,099	$ 6,099	$ 7,870
Notes and accounts receivable - trade, allowances	354	354	299
Contract assets	528	528	492
Deferred income (current)	11,681	11,681	12,026
Deferred income (noncurrent)	3,820	3,820	$ 3,851
Revenue recognized that was included in deferred income at the beginning of the period	$ 4,200	$ 8,600