XML 25 R121.htm IDEA: XBRL DOCUMENT v2.4.0.8
Unaudited Quarterly Financial Information Unaudited Quarterly Financial Information (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 12 Months Ended
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2012
Quarterly Financial Information Disclosure [Abstract]                      
Operating revenues $ 3,166 $ 2,651 $ 2,938 $ 2,382 $ 3,034 $ 2,602 $ 2,741 $ 2,579 $ 11,137 $ 10,956 $ 11,220
Operating expenses 2,569 2,453 2,362 2,164 2,276 2,324 2,380 2,523 9,548 9,503 9,920
Operating income 597 198 576 218 758 278 361 56 1,589 1,453 1,300
Net income (loss) $ 322 $ (81) $ 295 $ (67) $ 474 $ (12) $ 54 $ (245) $ 469 $ 271 $ 60