Fair Value Measurements (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	$ 321	$ 310
Derivatives	9	205
Total Assets at Fair Value	330	515
Derivatives	63	53
Total Liabilities at Fair Value	63	53
Level 1 [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	321	310
Derivatives	5	189
Total Assets at Fair Value	326	499
Derivatives	29	47
Total Liabilities at Fair Value	29	47
Level 2 [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	0	0
Derivatives	4	16
Total Assets at Fair Value	4	16
Derivatives	34	6
Total Liabilities at Fair Value	34	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