Revenue (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Credit memoranda issued	$ 37
Long-term liabilities	927	$ 922
Short-term liabilities	$ 104	54
Maximum [Member]
Long-term supply commitment	10 years
Accounting Standards Update 2014-09 [Member]
Customer deposits	$ 1,000	$ 1,000