Significant Accounting Policies and Methods of Application - Cost of Goods Sold Adjustments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Inventory [Line Items]
LOCOM adjustments	$ 23	$ 77	$ 9
Retail Operations [Member]
Inventory [Line Items]
LOCOM adjustments	3	4	1
Wholesale Services [Member]
Inventory [Line Items]
LOCOM adjustments	19	73	8
Other [Member]
Inventory [Line Items]
LOCOM adjustments	$ 1	$ 0	$ 0