Revenues and Segment Information, Geographic Information by Country for Revenue and Long-Lived Assets (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Operating Revenues by Geographic Area
Revenues	$ 27,879	$ 27,249	$ 28,933	$ 24,263	$ 28,730	$ 30,849	$ 31,015	$ 26,439	$ 108,324	[1]	$ 117,033	[1]	$ 93,980	[1]
Geographic Information by Country for Long-Lived Assets
Long-lived assets	31,100				30,652				31,100		30,652
U.S. [Member]
Operating Revenues by Geographic Area
Revenues									77,173		82,992		66,614
Geographic Information by Country for Long-Lived Assets
Long-lived assets	27,485				27,475				27,485		27,475
Canada [Member]
Operating Revenues by Geographic Area
Revenues									7,915		9,211		7,039
Geographic Information by Country for Long-Lived Assets
Long-lived assets	1,886				1,798				1,886		1,798
U.K.and Ireland [Member]
Operating Revenues by Geographic Area
Revenues									13,584		15,208		11,556
Geographic Information by Country for Long-Lived Assets
Long-lived assets	1,232				1,113				1,232		1,113
Other Countries [Member]
Operating Revenues by Geographic Area
Revenues									9,652		9,622		$ 8,771
Geographic Information by Country for Long-Lived Assets
Long-lived assets	$ 497				$ 266				$ 497		$ 266

[1] Includes excise taxes on sales by certain of our international operations of $5,595 million, $5,626 million, and $5,573 million for the years ended December 31, 2019, 2018, and 2017.