Financial Instruments (Non-Marketable Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Unrealized gains	$ 356	$ 456
Unrealized losses (including impairment)	(1,304)	(66)
Total unrealized gain (loss) for non-marketable equity securities	$ (948)	$ 390