Fair Value Measurements (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Fair Value Measurements [Line Items]
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ (313,000,000)	$ (635,000,000)	$ (1,400,000,000)	$ (1,100,000,000)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 435,000,000	$ 392,000,000	$ 1,700,000,000	$ 1,200,000,000
Weighted Average [Member] | Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Inventory Related Payables [Member]
Fair Value Measurements [Line Items]
Basis	14.50%		14.50%		13.70%
Weighted Average [Member] | Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Inventories Carried At Market [Member]
Fair Value Measurements [Line Items]
Basis	33.30%		33.30%		4.30%