Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 2,487	$ 2,176
Other Assets, Fair Value Disclosure	118	344
Fuel Contracts, Derivatives, Net	314	249
Interest Rate Derivatives, at Fair Value, Net	(67)	(66)
Foreign Currency Exchange Contracts, Hedge Derivatives, Net	257	123
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	2,487	2,176
Other Assets, Fair Value Disclosure	118	344
Fuel Contracts, Derivatives, Net	16	27
Interest Rate Derivatives, at Fair Value, Net	0	0
Foreign Currency Exchange Contracts, Hedge Derivatives, Net	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Other Assets, Fair Value Disclosure	0	0
Fuel Contracts, Derivatives, Net	298	222
Interest Rate Derivatives, at Fair Value, Net	(67)	(66)
Foreign Currency Exchange Contracts, Hedge Derivatives, Net	257	123
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Other Assets, Fair Value Disclosure	0	0
Fuel Contracts, Derivatives, Net	0	0
Interest Rate Derivatives, at Fair Value, Net	0	0
Foreign Currency Exchange Contracts, Hedge Derivatives, Net	0	0
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	959	958
Short-term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	959	958
Short-term Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Short-term Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0	0
Other Long-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	109	208
Other Long-term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	80	100
Other Long-term Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	29	27
Other Long-term Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	$ 0	$ 81
Cash and Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.
Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.
Other Long-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).
Fuel Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).
Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities; Income approach. Techniques to convert future amounts to a single present amount based on market expectations (including present value techniques, option-pricing and excess earnings models).
Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements, Valuation Techniques	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.	Market approach. Prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities.