Supplemental Financial Information - Other Assets (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Other Assets [Abstract]
Intangible assets	$ 132	$ 138
Non-current investments	43	41
Other	153	148
Other assets	583	633
Other Assets | Fuel derivatives
Other Assets [Abstract]
Asset derivative contracts, net	172	221
Other Assets | Interest rate derivatives
Other Assets [Abstract]
Asset derivative contracts, net	29	31
Other Noncurrent Assets | Fuel derivatives
Other Assets [Abstract]
Receivable from third parties for settled fuel contracts - noncurrent	$ 54	$ 54