Commitments and Contingencies - Environmental Matters (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Method
Environmental Matters  
Accrued environmental remediation costs $ 1
Maximum exposure 1
Number of estimation methodologies 2
Climate Change and Other Emissions  
Environmental Matters  
Number of major sources of other "criteria" pollutant 6
Maximum | Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) Matters  
Environmental Matters  
Accrued environmental remediation costs $ 1