Financial Instruments (Non-Marketable Equity Securities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Unrealized gains	$ 2,163	$ 4,285
Unrealized losses (including impairment)	(372)	(178)
Total unrealized gain (loss) for non-marketable equity securities	$ 1,791	$ 4,107