Disclosures About Segments And Related Information (Schedule Of Long-Lived Assets By Geographic Regions) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Long-lived assets	$ 251,605	$ 252,668	$ 243,650
U.S. [Member]
Long-lived assets	107,039	104,000	98,271
Non-U.S. [Member]
Long-lived assets	144,566	148,668	145,379
Canada [Member]
Long-lived assets	39,775	43,858	41,522
Australia [Member]
Long-lived assets	15,894	15,328	14,258
Nigeria [Member]
Long-lived assets	12,222	12,265	12,343
Kazakhstan [Member]
Long-lived assets	9,705	9,138	8,530
Singapore [Member]
Long-lived assets	9,681	9,620	9,570
Angola [Member]
Long-lived assets	8,777	9,057	8,262
Papua New Guinea [Member]
Long-lived assets	$ 5,985	$ 6,099	$ 5,768