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Other Assets, Net (Details 2) (USD $)
In Millions, unless otherwise specified
 12 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2013
Customer contracts and relationships
Dec. 31, 2012
Customer contracts and relationships
Dec. 31, 2013
Customer contracts and relationships
Minimum
Dec. 31, 2013
Customer contracts and relationships
Maximum
Dec. 31, 2013
Property tax abatement
Dec. 31, 2012
Property tax abatement
Dec. 31, 2013
Property tax abatement
Minimum
Dec. 31, 2013
Property tax abatement
Maximum
Dec. 31, 2013
Other agreements
Dec. 31, 2012
Other agreements
Dec. 31, 2013
Other agreements
Minimum
Dec. 31, 2013
Other agreements
Maximum
Dec. 31, 2013
Emission reduction credits
Dec. 31, 2012
Emission reduction credits
Finite-Lived Intangible Assets                                
Estimated Useful Lives         1 year 20 years     7 years 13 years     25 years 70 years    
Cost $ 674 $ 642 $ 591 $ 558     $ 38 $ 38     $ 37 $ 38     $ 8 $ 8
Accumulated amortization (254) (169) (237) (157)     (14) (10)     (3) (2)        
Net 420 473 354 401     24 28     34 36     8 8
Estimated amortization expense related to finite-lived intangible assets for the next five years                                
2014 59                              
2015 52                              
2016 45                              
2017 42                              
2018 $ 36