Fair Value Measurements (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	$ 320	$ 310
Derivatives	23	205
Total Assets at Fair Value	343	515
Derivatives	74	53
Total Liabilities at Fair Value	74	53
Level 1 [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	320	310
Derivatives	4	189
Total Assets at Fair Value	324	499
Derivatives	69	47
Total Liabilities at Fair Value	69	47
Level 2 [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	0	0
Derivatives	19	16
Total Assets at Fair Value	19	16
Derivatives	5	6
Total Liabilities at Fair Value	5	6
Level 3 [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	0	0
Derivatives	0	0
Total Assets at Fair Value	0	0
Derivatives	0	0
Total Liabilities at Fair Value	$ 0	$ 0