Summary Of Significant Accounting Policies (Schedule Of Inventories) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Document Period End Date	Dec. 31, 2019
LIFO inventories
FIFO value	$ 1,022	$ 1,010
LIFO valuation reserve	(91)	(54)
LIFO inventories carrying value	931	956
FIFO inventories	3,106	2,908
Market inventories	4,704	4,547
Supplies and other inventories	429	402
Total inventories	$ 9,170	$ 8,813