Financial Derivative Instruments - Fuel Hedging (Details)	Jun. 30, 2014 gal
Remainder of 2014
Volume of Fuel Hedging [Line Items]
Fuel Hedged (in gallons)	365,000,000	[1]
2015
Volume of Fuel Hedging [Line Items]
Fuel Hedged (in gallons)	1,165,000,000	[1]
2016
Volume of Fuel Hedging [Line Items]
Fuel Hedged (in gallons)	1,089,000,000	[1]
2017
Volume of Fuel Hedging [Line Items]
Fuel Hedged (in gallons)	820,000,000	[1]
2018
Volume of Fuel Hedging [Line Items]
Fuel Hedged (in gallons)	98,000,000	[1]

[1] The Company determined gallons hedged based on market prices and forward curves as of June 30, 2014. Due to the types of derivatives utilized by the Company, these volumes represent the maximum economic hedge in place and may vary significantly as market prices fluctuate.