Debt - Components (Details) - USD ($) $ in Millions	Mar. 31, 2017	Jan. 31, 2017	Dec. 31, 2016
Short-term debt:
Total short-term debt	$ 1,341		$ 1,715
Long-term debt:
Senior notes, net of unamortized discounts and debt issuance costs of $74 and $76, respectively	9,876		9,874
Other long-term debt	3		250
Total long-term debt	9,879		10,124
Total debt	11,220		$ 11,839
Commercial paper notes
Long-term debt:
Weighted average interest rate, long-term			1.60%
Other long-term debt			$ 247
Senior notes
Long-term debt:
Unamortized discounts and debt issuance costs	74		76
Senior notes, net of unamortized discounts and debt issuance costs of $74 and $76, respectively	9,876		9,874
Other
Long-term debt:
Other long-term debt	$ 3		$ 3
Commercial paper notes
Short-term debt:
Weighted average interest rate, short-term	1.90%		1.60%
Short-term debt	$ 958		$ 563
Other
Short-term debt:
Other short-term debt	$ 133		$ 2
Senior secured hedged inventory facility | Credit facility
Short-term debt:
Weighted average interest rate, short-term	2.00%		1.80%
Short-term debt	$ 250		$ 750
6.13% senior notes due January 2017 | Senior notes
Short-term debt:
Debt instrument, interest rate		6.13%	6.13%
Senior notes, current			$ 400