Hedging Hedge Portfolio Table (Details) In Millions, unless otherwise specified	36 Months Ended
	Sep. 30, 2015	Sep. 30, 2013 Purchased euro put options settling in 2013 [Member] USD ($)	Sep. 30, 2013 Purchased euro put options settling in 2013 [Member] EUR (€)	Jun. 30, 2013 Purchased euro put options settling in 2013 [Member] USD ($)	Jun. 30, 2013 Purchased euro put options settling in 2013 [Member] EUR (€)	Mar. 31, 2013 Purchased euro put options settling in 2013 [Member] USD ($)	Mar. 31, 2013 Purchased euro put options settling in 2013 [Member] EUR (€)	Sep. 30, 2013 Sold euro call options settling in 2013 [Member] USD ($)	Sep. 30, 2013 Sold euro call options settling in 2013 [Member] EUR (€)	Jun. 30, 2013 Sold euro call options settling in 2013 [Member] USD ($)	Jun. 30, 2013 Sold euro call options settling in 2013 [Member] EUR (€)	Mar. 31, 2013 Sold euro call options settling in 2013 [Member] USD ($)	Mar. 31, 2013 Sold euro call options settling in 2013 [Member] EUR (€)	Mar. 31, 2013 Average rate forward contracts settling in 2013 [Domain] [Domain] USD ($)	Mar. 31, 2013 Average rate forward contracts settling in 2013 [Domain] [Domain] EUR (€)	Jun. 30, 2014 Purchased euro put options settling in 2014 [Member] [Member] USD ($)	Mar. 31, 2013 Purchased euro put options settling in 2014 [Member] [Member] USD ($)	Jun. 30, 2014 Average rate forward contracts settling in 2014 [Domain] [Domain] [Member] USD ($)	Mar. 31, 2013 Average rate forward contracts settling in 2014 [Domain] [Domain] [Member] USD ($)	Jun. 30, 2014 Sold euro call options settling in 2014 [Member] [Member] USD ($)	Mar. 31, 2013 Sold euro call options settling in 2014 [Member] [Member] USD ($)	Mar. 31, 2013 2013 [Member] Mg	Mar. 31, 2013 2014 [Member] Mg	Mar. 31, 2013 2015 [Member] Mg	Mar. 31, 2013 30 day euro forward contract [Member] USD ($)	Mar. 31, 2013 30 day euro forward contract [Member] EUR (€)
Derivative [Line Items]
Maximum Length of Time Hedged in Price Risk Cash Flow Hedge	3 years
Notional amount of currency derivatives designated cash flow hedges							€ 108						€ 108		€ 108		$ 54		$ 54		$ 54
Notional amount of fuel derivatives designated cash flow hedges																						57,525	108,416	74,640
Fuel derivatives designated cash flow hedges contract average rate (in USD per mt)																						506	587	564
Currency derivatives designated cash flow hedges contract average of price (in USD per euro)		1.20		1.20		1.20		1.28		1.28		1.28		1.23		1.30		1.33		1.38
Notional amount of foreign currency derivative instruments not designated as hedging instruments			€ 27		€ 19				€ 27		€ 19															€ 73
Foreign currency derivative instruments not designated as hedging instruments average forward exchange rate																									1.28