Summary Of Significant Accounting Policies Summary Of Significant Accounting Policies (Schedule Of Inventories) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
LIFO inventories
FIFO value	$ 1,077	$ 1,199
LIFO valuation reserve	(56)	(53)
LIFO inventories carrying value	1,021	1,146
FIFO inventories	2,756	3,058
Market inventories	4,066	4,699
Supplies and other inventories	400	471
Total inventories	$ 8,243	$ 9,374