Derivatives (Details) In Millions, unless otherwise specified																															6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended		12 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)	Jun. 30, 2014 Prepaid Expenses and Other [Member] USD ($)	Dec. 31, 2013 Prepaid Expenses and Other [Member] USD ($)	Jun. 30, 2014 Other Noncurrent Assets [Member] USD ($)	Dec. 31, 2013 Other Noncurrent Assets [Member] USD ($)	Jun. 30, 2014 Other Accrued Liabilities [Member] USD ($)	Dec. 31, 2013 Other Accrued Liabilities [Member] USD ($)	Jun. 30, 2014 Other Noncurrent Liabilities [Member] USD ($)	Dec. 31, 2013 Other Noncurrent Liabilities [Member] USD ($)	Jun. 30, 2014 Designated as Hedging Instrument [Member] USD ($)	Dec. 31, 2013 Designated as Hedging Instrument [Member] USD ($)	Jun. 30, 2014 Designated as Hedging Instrument [Member] Prepaid Expenses and Other [Member] USD ($)	Dec. 31, 2013 Designated as Hedging Instrument [Member] Prepaid Expenses and Other [Member] USD ($)	Jun. 30, 2014 Designated as Hedging Instrument [Member] Other Noncurrent Assets [Member] USD ($)	Dec. 31, 2013 Designated as Hedging Instrument [Member] Other Noncurrent Assets [Member] USD ($)	Jun. 30, 2014 Designated as Hedging Instrument [Member] Other Accrued Liabilities [Member] USD ($)	Dec. 31, 2013 Designated as Hedging Instrument [Member] Other Accrued Liabilities [Member] USD ($)	Jun. 30, 2014 Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member] USD ($)	Dec. 31, 2013 Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member] USD ($)	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] USD ($)	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] USD ($)	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Prepaid Expenses and Other [Member] USD ($)	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Prepaid Expenses and Other [Member] USD ($)	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Other Noncurrent Assets [Member] USD ($)	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Other Noncurrent Assets [Member] USD ($)	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Other Accrued Liabilities [Member] USD ($)	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Other Accrued Liabilities [Member] USD ($)	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member] USD ($)	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member] USD ($)	Jun. 30, 2014 Fuel Contracts [Member] Not Designated as Hedging Instrument [Member] gal	Dec. 31, 2013 Fuel Contracts [Member] Not Designated as Hedging Instrument [Member] gal	Jun. 30, 2014 Cash Flow Hedging [Member] Interest Rate Contract [Member] Designated as Hedging Instrument [Member] USD ($)	Dec. 31, 2013 Cash Flow Hedging [Member] Interest Rate Contract [Member] Designated as Hedging Instrument [Member] USD ($)	Jun. 30, 2014 Cash Flow Hedging [Member] Foreign Currency Exchange Contracts [Member] Designated as Hedging Instrument [Member] CAD	Jun. 30, 2014 Cash Flow Hedging [Member] Foreign Currency Exchange Contracts [Member] Designated as Hedging Instrument [Member] JPY (¥)	Dec. 31, 2013 Cash Flow Hedging [Member] Foreign Currency Exchange Contracts [Member] Designated as Hedging Instrument [Member] CAD	Dec. 31, 2013 Cash Flow Hedging [Member] Foreign Currency Exchange Contracts [Member] Designated as Hedging Instrument [Member] JPY (¥)	Jun. 30, 2014 Fair Value Hedging [Member] Interest Rate Contract [Member] Designated as Hedging Instrument [Member] USD ($)	Dec. 31, 2013 Fair Value Hedging [Member] Interest Rate Contract [Member] Designated as Hedging Instrument [Member] USD ($)
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount																																	$ 234	$ 477	448	¥ 111,262	438	¥ 120,915	$ 430	$ 445
Derivative, Nonmonetary Notional Amount																															4,229,000,000	5,318,000,000
Derivative, Final Maturity Date																															Dec. 31, 2015	Mar. 31, 2015	May 31, 2019	May 31, 2019	Jan. 05, 2017	Jan. 05, 2017	Aug. 31, 2016	Aug. 31, 2016	Aug. 31, 2022	Aug. 31, 2022
Interest Rate Contracts (Cash Flow Hedges), Assets													0	0	0	0
Interest Rate Contracts (Cash Flow Hedges), Liabilities																	(8)	(17)	(12)	(26)
Interest Rate Contracts (Cash Flow Hedges), Hedge Derivatives, Net											(20)	(43)
Interest Rate Contracts (Fair Value Hedges), Assets													0	0	0	0
Interest Rate Contracts (Fair Value Hedges), Liabilities																	(2)	(2)	(11)	(22)
Interest Rate Contracts (Fair Value Hedges), Hedge Derivatives, Net											(13)	(24)
Foreign Currency Exchange Contracts, Assets													109	157	44	100
Foreign Currency Exchange Contracts, Liabilities																	(2)	0	(5)	0
Foreign Currency Exchange Contracts, Hedge Derivatives, Net	146	257									146	257
Fuel Hedge Contracts, Assets																							411	428	14	29
Fuel Hedge Contracts, Liabilities																											(165)	(127)	(5)	(16)
Fuel Hedge Contracts, Derivatives, Net	255	314																			255	314
Total Derivative Contracts, Assets			520	585	58	129
Total Derivative Contracts, Liabilities							(177)	(146)	(33)	(64)
Net Derivative Contracts, Assets			355	456	52	116
Net Derivative Contracts, Liabilities							(11)	(19)	(28)	(49)
Net Derivative Contracts, Hedge Derivatives, Net	$ 368	$ 504