Accounting Standards - Revenue Recognition Standard (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues and other income:
Revenues from contracts with customers	$ 1,537	$ 873
Marketing revenues	0	34
Other income	4	14
Costs and expenses:
Marketing, including purchases from related parties	0	34
Other operating	130	$ 89
Presentation without adoption of ASC Topic 606 [Member]
Revenues and other income:
Revenues from contracts with customers	1,433
Marketing revenues	32
Other income	3
Costs and expenses:
Marketing, including purchases from related parties	32
Other operating	127
Accounting Standards Update 2014-09 [Member] | Adjustments [Member]
Revenues and other income:
Revenues from contracts with customers	(104)
Marketing revenues	32
Other income	(1)
Costs and expenses:
Marketing, including purchases from related parties	32
Other operating	$ (3)