Financial Instruments (Carrying Amount of Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]
Total sale price	$ 1,389	$ 445	$ 2,888	$ 1,074
Total initial cost	1,146	133	1,831	460
Cumulative net gains	243	$ 312	1,057	$ 614
Total initial cost, marketable securities	2,438		2,438		$ 1,935
Cumulative net gain, marketable securities	2,596		2,596		1,361
Carrying value, marketable securities	5,034		5,034		3,296
Total initial cost, non-marketable securities	9,615		9,615		8,297
Cumulative net gain, non-marketable securities	3,304		3,304		3,056
Carrying value, non-marketable securities	12,919		12,919		11,353
Total initial cost	12,053		12,053		10,232
Cumulative net gain	5,900		5,900		4,417
Carrying value	17,953		17,953		14,649
Cumulative net gain of non-marketable securities	5,100		5,100		3,500
Unrealized loss of non-marketable securities	1,800		1,800		$ 445
Other Noncurrent Assets
Debt and Equity Securities, FV-NI [Line Items]
Carrying value, marketable securities	$ 447		$ 447