Segment Disclosures Geographic Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from external customers:
Revenues from external customers	$ 7,360	$ 7,637	$ 6,860
Long-lived assets:
Long-lived assets	39,596	39,654	20,500
United States [Member]
Revenues from external customers:
Revenues from external customers	7,247	7,229	6,703
Long-lived assets:
Long-lived assets	38,016	38,290	19,260
Canada [Member]
Revenues from external customers:
Revenues from external customers	113	408	157
Long-lived assets:
Long-lived assets	$ 1,580	$ 1,364	$ 1,240