XML 176 R122.htm IDEA: XBRL DOCUMENT v3.5.0.2
Unaudited Quarterly Financial Information Unaudited Quarterly Financial Information (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2014
Quarterly Financial Information Disclosure [Abstract]                      
Operating revenues $ 3,286 $ 2,479 $ 2,571 $ 2,280 $ 3,171 $ 2,558 $ 2,863 $ 2,411 $ 10,616 $ 11,003 $ 11,137
Operating expenses 2,343 1,913 1,982 2,052 2,402 2,252 2,087 2,047 8,290 8,788 9,548
Operating income 943 566 589 228 769 306 776 364 2,326 2,215 1,589
Net income (loss) $ 661 $ 291 $ 318 $ (37) $ 502 $ 32 $ 496 $ 81 $ 1,233 $ 1,111 $ 469