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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Operating Revenues by Geographic Area
Revenues	$ 28,730	$ 30,849	$ 31,015	$ 26,439	$ 26,392	[1]	$ 23,562	$ 22,254	$ 21,772	$ 117,033	[2]	$ 93,980	[2]	$ 75,659	[2]
Geographic Information by Country for Long-Lived Assets
Long-lived assets	30,652				29,061					30,652		29,061
U.S. [Member]
Operating Revenues by Geographic Area
Revenues										82,992		66,614		51,479
Geographic Information by Country for Long-Lived Assets
Long-lived assets	27,475				26,083					27,475		26,083
Canada [Member]
Operating Revenues by Geographic Area
Revenues										9,211		7,039		6,115
Geographic Information by Country for Long-Lived Assets
Long-lived assets	1,798				1,915					1,798		1,915
U.K.and Ireland [Member]
Operating Revenues by Geographic Area
Revenues										15,208		11,556		10,797
Geographic Information by Country for Long-Lived Assets
Long-lived assets	1,113				1,063					1,113		1,063
Other Countries [Member]
Operating Revenues by Geographic Area
Revenues										9,622		8,771		$ 7,268
Geographic Information by Country for Long-Lived Assets
Long-lived assets	$ 266				$ 0					$ 266		$ 0

[1] During the quarter ended December 31, 2017, we recognized an income tax benefit of $1.9 billion related to Tax Reform as described in Note 15.

[2] Includes excise taxes on sales by certain of our international operations of $5,626 million, $5,573 million, and $5,493 million for the years ended December 31, 2018, 2017, and 2016.