XML 35 R28.htm IDEA: XBRL DOCUMENT v2.4.0.6
Inventory (Tables)
3 Months Ended
Mar. 31, 2013
Inventory Tables [Abstract]  
Inventory Balance By Type
  March 31, December 31,
  2013 2012
       
  (in millions)
Coal, fuel oil and other raw materials $ 363 $ 373
Spare parts and supplies   392   393
Total $ 755 $ 766