Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Derivatives	$ 43	$ 32
Derivatives	11	109
Recurring Basis
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	13	13
Derivatives	43	32
Total Assets at Fair Value	56	45
Derivatives	11	109
Total Liabilities at Fair Value	11	109
Recurring Basis | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	13	13
Derivatives	31	15
Total Assets at Fair Value	44	28
Derivatives	1	78
Total Liabilities at Fair Value	1	78
Recurring Basis | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	0	0
Derivatives	12	17
Total Assets at Fair Value	12	17
Derivatives	10	31
Total Liabilities at Fair Value	10	31
Recurring Basis | Level 3
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