Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements and Derivatives - Additional Information (Detail)

v2.4.0.6
Fair Value Measurements and Derivatives - Additional Information (Detail)
In Millions, unless otherwise specified
3 Months Ended 3 Months Ended
Mar. 31, 2013
USD ($)
Dec. 31, 2012
USD ($)
Mar. 31, 2013
Fuel Swaps
Mg
Mar. 31, 2013
Fuel Swaps
Maximum
Mar. 31, 2013
Fuel Collars and Fuel Options
Mg
Mar. 31, 2013
Fuel Collars and Fuel Options
Maximum
Mar. 31, 2013
Foreign Exchange Option
USD ($)
Mar. 31, 2013
Foreign Exchange Option
EUR (€)
Mar. 31, 2013
Foreign Exchange Forward
USD ($)
Mar. 31, 2013
Foreign Exchange Forward
EUR (€)
Mar. 31, 2013
Foreign Currency Collar
USD ($)
Mar. 31, 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     484,000   61,000              
Notional amount of foreign currency derivatives             $ 224.3 € 175.0 $ 598.6 € 467.0 $ 128.2 € 100.0
Fair value of long-term debt 2,747.8 3,106.9                    
Fair value of long-term debt in excess of carrying value $ 109.5 $ 121.5