XML 38 R47.htm IDEA: XBRL DOCUMENT v3.3.0.814
Inventory (Details) - USD ($)
$ in Millions
Sep. 30, 2015
Dec. 31, 2014
Inventory Disclosure [Abstract]    
Fuel and other raw materials $ 336 $ 357
Spare parts and supplies 334 345
Total $ 670 $ 702