|
Fair Value Measurements and Derivatives - Additional Information (Detail)
In Millions, unless otherwise specified |
6 Months Ended | 6 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
|
Jun. 30, 2013
USD ($)
|
Dec. 31, 2012
USD ($)
|
Jun. 30, 2013
Fuel Swaps
Mg
|
Jun. 30, 2013
Fuel Swaps
Maximum
|
Jun. 30, 2013
Fuel Collars and Fuel Options
Mg
|
Jun. 30, 2013
Fuel Collars and Fuel Options
Maximum
|
Jun. 30, 2013
Foreign Exchange Option
USD ($)
|
Jun. 30, 2013
Foreign Exchange Option
EUR (€)
|
Jun. 30, 2013
Foreign Currency Collar
USD ($)
|
Jun. 30, 2013
Foreign Currency Collar
EUR (€)
|
|
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||||||||||
| Derivative maturing date | Dec. 31, 2015 | Dec. 31, 2014 | ||||||||
| Projected fuel purchases | 761,000 | 52,000 | ||||||||
| Notional amount of foreign currency derivatives | $ 227.7 | € 175.0 | $ 130.1 | € 100.0 | ||||||
| Fair value of long-term debt | 3,093.2 | 3,106.9 | ||||||||
| Fair value of long-term debt in excess of carrying value | $ 98.0 | $ 121.5 | ||||||||