Derivatives (Details) In Millions, unless otherwise specified																															9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended		12 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)	Sep. 30, 2013 Prepaid Expenses and Other [Member] USD ($)	Dec. 31, 2012 Prepaid Expenses and Other [Member] USD ($)	Sep. 30, 2013 Other Noncurrent Assets [Member] USD ($)	Dec. 31, 2012 Other Noncurrent Assets [Member] USD ($)	Sep. 30, 2013 Other Accrued Liabilities [Member] USD ($)	Dec. 31, 2012 Other Accrued Liabilities [Member] USD ($)	Sep. 30, 2013 Other Noncurrent Liabilities [Member] USD ($)	Dec. 31, 2012 Other Noncurrent Liabilities [Member] USD ($)	Sep. 30, 2013 Designated as Hedging Instrument [Member] USD ($)	Dec. 31, 2012 Designated as Hedging Instrument [Member] USD ($)	Sep. 30, 2013 Designated as Hedging Instrument [Member] Prepaid Expenses and Other [Member] USD ($)	Dec. 31, 2012 Designated as Hedging Instrument [Member] Prepaid Expenses and Other [Member] USD ($)	Sep. 30, 2013 Designated as Hedging Instrument [Member] Other Noncurrent Assets [Member] USD ($)	Dec. 31, 2012 Designated as Hedging Instrument [Member] Other Noncurrent Assets [Member] USD ($)	Sep. 30, 2013 Designated as Hedging Instrument [Member] Other Accrued Liabilities [Member] USD ($)	Dec. 31, 2012 Designated as Hedging Instrument [Member] Other Accrued Liabilities [Member] USD ($)	Sep. 30, 2013 Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member] USD ($)	Dec. 31, 2012 Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member] USD ($)	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] USD ($)	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] USD ($)	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Prepaid Expenses and Other [Member] USD ($)	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Prepaid Expenses and Other [Member] USD ($)	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Other Noncurrent Assets [Member] USD ($)	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Other Noncurrent Assets [Member] USD ($)	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Other Accrued Liabilities [Member] USD ($)	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Other Accrued Liabilities [Member] USD ($)	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member] USD ($)	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member] USD ($)	Sep. 30, 2013 Fuel Contracts [Member] Not Designated as Hedging Instrument [Member] gal	Dec. 31, 2012 Fuel Contracts [Member] Not Designated as Hedging Instrument [Member] gal	Sep. 30, 2013 Cash Flow Hedging [Member] Interest Rate Contracts [Member] Designated as Hedging Instrument [Member] USD ($)	Dec. 31, 2012 Cash Flow Hedging [Member] Interest Rate Contracts [Member] Designated as Hedging Instrument [Member] USD ($)	Sep. 30, 2013 Cash Flow Hedging [Member] Foreign Currency Exchange Contracts [Member] Designated as Hedging Instrument [Member] CAD	Sep. 30, 2013 Cash Flow Hedging [Member] Foreign Currency Exchange Contracts [Member] Designated as Hedging Instrument [Member] JPY (¥)	Dec. 31, 2012 Cash Flow Hedging [Member] Foreign Currency Exchange Contracts [Member] Designated as Hedging Instrument [Member] CAD	Dec. 31, 2012 Cash Flow Hedging [Member] Foreign Currency Exchange Contracts [Member] Designated as Hedging Instrument [Member] JPY (¥)	Sep. 30, 2013 Fair Value Hedging [Member] Interest Rate Contracts [Member] Designated as Hedging Instrument [Member] USD ($)	Dec. 31, 2012 Fair Value Hedging [Member] Interest Rate Contracts [Member] Designated as Hedging Instrument [Member] USD ($)
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount																																	$ 588	$ 740	508	¥ 128,713	430	¥ 119,277	$ 445	$ 469
Derivative, Final Maturity Date																															Dec. 31, 2014	Dec. 31, 2013	May 31, 2019	May 31, 2019	Aug. 31, 2016	Aug. 31, 2016	Dec. 31, 2015	Dec. 31, 2015	Aug. 31, 2022	Aug. 31, 2022
Derivative, Nonmonetary Notional Amount																															4,110,000,000	1,792,000,000
Interest Rate Contracts (Cash Flow Hedges), Assets													0	0	0	0
Interest Rate Contracts (Cash Flow Hedges), Liabilities																	(18)	(22)	(30)	(48)
Interest Rate Contracts (Cash Flow Hedges), Hedge Derivatives, Net											(48)	(70)
Interest Rate Contracts (Fair Value Hedges), Assets													5	0	0	6
Interest Rate Contracts (Fair Value Hedges), Liabilities																	0	(2)	(23)	0
Interest Rate Contracts (Fair Value Hedges), Hedge Derivatives, Net											(18)	4
Foreign Currency Exchange Contracts, Assets													118	62	76	63
Foreign Currency Exchange Contracts, Liabilities																	0	(1)	(1)	(1)
Foreign Currency Exchange Contracts, Hedge Derivatives, Net	193	123									193	123
Fuel Contracts, Assets																							487	511	10	0
Fuel Contracts, Liabilities																											(160)	(262)	(4)	0
Fuel Contracts, Derivatives, Net	333	249																			333	249
Total Derivative Contracts, Assets			610	573	86	69
Total Derivative Contracts, Liabilities							(178)	(287)	(58)	(49)
Net Derivative Contracts, Assets			457	320	84	69
Net Derivative Contracts, Liabilities							(28)	(34)	(53)	(49)
Net Derivative Contracts, Hedge Derivatives, Net	$ 460	$ 306