Segment Information, Geographic Information by Country for Revenue and Long-Lived Assets (Details) - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Operating revenues by geographic area
Operating revenues	$ 18,777	[1]	$ 22,579	$ 25,118	$ 21,330	$ 27,859	$ 34,408	$ 34,914	$ 33,663	$ 87,804	[2]	$ 130,844	[2]	$ 138,074	[2]
Geographic information by country for long-lived assets
Long-lived assets	28,242					28,094				28,242		28,094
U.S. [Member]
Operating revenues by geographic area
Operating revenues										60,319		91,499		100,418
Geographic information by country for long-lived assets
Long-lived assets	25,210					24,653				25,210		24,653
Canada [Member]
Operating revenues by geographic area
Operating revenues										6,841		10,410		9,974
Geographic information by country for long-lived assets
Long-lived assets	1,824					2,161				1,824		2,161
U.K.and Ireland [Member]
Operating revenues by geographic area
Operating revenues										11,232		14,182		13,675
U.K. [Member]
Geographic information by country for long-lived assets
Long-lived assets	1,131					1,199				1,131		1,199
Other Countries [Member]
Operating revenues by geographic area
Operating revenues										9,412		14,753		$ 14,007
Aruba [Member]
Geographic information by country for long-lived assets
Long-lived assets	57					59				57		59
Ireland [Member]
Geographic information by country for long-lived assets
Long-lived assets	$ 20					$ 22				$ 20		$ 22

[1] Operating income for the quarter ended December 31, 2015 reflects a noncash lower of cost or market inventory valuation adjustment of $790 million, as described in Note 6.

[2] Includes excise taxes on sales by certain of our international operations of $5,980 million, $5,901 million, and $5,459 million.