Annual report pursuant to Section 13 and 15(d)

Derivatives and Hedging - Additional Information (Detail)

v2.4.0.6
Derivatives and Hedging - Additional Information (Detail)
 12 Months Ended 5 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2011
USD ($)
May 28, 2010
Predecessor [Member]
USD ($)
Aug. 29, 2008
2008 Swap [Member]
USD ($)
Dec. 31, 2012
2010 Swap [Member]
USD ($)
Dec. 31, 2011
2010 Swap [Member]
USD ($)
Jun. 24, 2010
2010 Swap [Member]
USD ($)
Dec. 31, 2012
2012 Metal Swap No.1 [Member]
USD ($)
Apr. 20, 2012
2012 Metal Swap No.1 [Member]
USD ($)
Mg
Dec. 31, 2012
2012 Metal Swap No. 2 [Member]
USD ($)
May 30, 2012
2012 Metal Swap No. 2 [Member]
USD ($)
Mg
Dec. 31, 2012
2012 Metal Swap No.3 [Member]
USD ($)
May 30, 2012
2012 Metal Swap No.3 [Member]
USD ($)
Mg
Dec. 31, 2012
2012 FX Contract [Member]
USD ($)
Dec. 18, 2012
2012 FX Contract [Member]
CAD
Derivative [Line Items]                            
Term of derivative instrument     3 years     2 years   8 months   7 months   10 months   6 months
Notional amount of derivative instrument     $ 50,000,000     $ 115,000,000   $ 294,700   $ 77,900   $ 272,500   105,000,000
Interest rate of derivative instrument     3.41%     2.47%                
Interest expense   1,579,000                        
Start date of forward derivative       May 31, 2011                    
Termination date of derivative       May 31, 2013     Dec. 31, 2012   Dec. 31, 2012   Mar. 31, 2013   May 21, 2013  
Unrealized gain(loss) on derivative 643,000                          
Fair value of derivative liability       (418,000)     17,000   (6,000)   (6,000)   (1,475,000)  
Fair value of derivative liability, non-current         $ (1,205,000)                  
Quantity of derivative instrument               35   10   35    
Price of copper               8.420   7.790   7.785    
Forward exchange rate                           0.9989