Quarterly report pursuant to sections 13 or 15(d)

Equity-Based Compensation - Summary of Equity Grants (Detail)

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Equity-Based Compensation - Summary of Equity Grants (Detail) (USD $)
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Performance Units
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Units 238,371 257,795
Granted, Units     
Vested, Units (140,549)  
Forfeited, Units (851) (8,761)
Ending Balance, Units 96,971 249,034
Beginning Balance, Fair Value per unit $ 3.75 $ 3.27
Granted, Fair Value per unit $ 0   
Vested, Fair Value per unit $ 0  
Forfeited, Fair Value per unit   $ (4.78)
Ending Balance, Fair Value per unit $ 3.75 $ 4.78
Deferred Equity Units
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Units 175,298 329,757
Granted, Units     
Vested, Units (123,110) (133,867)
Ending Balance, Units 52,188 195,890
Beginning Balance, Fair Value per unit   $ 10.47
Granted, Fair Value per unit     
Vested, Fair Value per unit   $ (15.30)
Ending Balance, Fair Value per unit   $ 15.30
Deferred Equity Units | Minimum
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Fair Value per unit $ 12.00  
Vested, Fair Value per unit $ (12.00)  
Ending Balance, Fair Value per unit $ 12.00  
Deferred Equity Units | Maximum
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Fair Value per unit $ 17.05  
Vested, Fair Value per unit $ (16.81)  
Ending Balance, Fair Value per unit $ 18.29