Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Derivatives	$ 82	$ 86
Derivatives	86	149
Fair Value, Measurements, Recurring [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	258	266
Derivatives	82	86
Total Assets at Fair Value	340	352
Derivatives	86	149
Total Liabilities at Fair Value	86	149
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	258	266
Derivatives	26	21
Total Assets at Fair Value	284	287
Derivatives	86	148
Total Liabilities at Fair Value	86	148
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	0	0
Derivatives	56	65
Total Assets at Fair Value	56	65
Derivatives	0	1
Total Liabilities at Fair Value	0	1
Level 3 [Member] | Fair Value, Measurements, Recurring [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