Financial Instruments (Carrying Amount of Equity Securities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Total sale price	$ 3,134	$ 1,965
Total initial cost	858	515
Cumulative net gains	2,276	1,450
Total initial cost, Marketable Securities	1,935	1,168
Cumulative net gain, Marketable Securities	1,361	54
Carrying value, Marketable Securities	3,296	1,222
Total initial cost, Non-Marketable Securities	8,297	8,168
Cumulative net gain, Non-Marketable Securities	3,056	4,107
Carrying value, Non-Marketable Securities	11,353	12,275
Total initial cost	10,232	9,336
Cumulative net gain	4,417	4,161
Carrying value	14,649	13,497
Cumulative net gain	3,500	4,300
Unrealized losses (including impairment)	$ 445	$ 178