Financial Instruments (Non-Marketable Equity Securities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Unrealized gains	$ 3,020	$ 2,163
Unrealized losses (including impairment)	(1,489)	(372)
Total unrealized gain (loss) for non-marketable equity securities	$ 1,531	$ 1,791