Supplemental Financial Information - Other Assets (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Other Assets [Abstract]
Intangible assets	$ 127	$ 138
Non-current investments	41	41
Other	158	148
Other assets	384	633
Other Assets | Fuel derivatives
Other Assets [Abstract]
Asset derivative contracts, net	9	221
Receivable from third parties for settled fuel contracts - noncurrent	27	54
Other Assets | Interest rate derivatives
Other Assets [Abstract]
Asset derivative contracts, net	22	31
Other Noncurrent Assets | Fuel derivatives
Other Assets [Abstract]
Receivable from third parties for settled fuel contracts - noncurrent	$ 27	$ 54