Significant Accounting Policies and Methods of Application - Changes in Amount of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Roll Forward]
Goodwill - December 31, 2014	$ 1,827
Impairment	(14)	$ 0	$ 0
Goodwill - December 31, 2015	1,813	1,827
Distribution Operations [Member]
Goodwill [Roll Forward]
Goodwill - December 31, 2014	1,640
Impairment	0
Goodwill - December 31, 2015	1,640	1,640
Retail Operations [Member]
Goodwill [Roll Forward]
Goodwill - December 31, 2014	173
Impairment	0
Goodwill - December 31, 2015	173	173
Midstream Operations [Member]
Goodwill [Roll Forward]
Goodwill - December 31, 2014	14
Impairment	(14)
Goodwill - December 31, 2015	$ 0	$ 14