Derivative Instruments and Hedging Activities (Assets and Liabilities - Current vs. Noncurrent Derivative instruments) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative Asset, Current		$ 99	$ 86
Derivative Liability, Current		155	144
Derivative Asset, Noncurrent		277	289
Derivative Liability, Noncurrent		269	346
Total asset derivatives		376	375
Total liability derivatives		424	490
Contracts Subject To Netting Arrangements
Derivatives, Fair Value [Line Items]
Total asset derivatives	[1]	41
Total liability derivatives	[1]		58
Derivative Assets Not Offset Under Netting Arrangements	[1]	$ 18
Derivative Liabilities Not Offset Under Netting Arrangements	[1]		$ 38

[1] Based on the credit rating of certain subsidiaries