Annual report pursuant to section 13 and 15(d)

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

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Equity-Based Compensation - Summary of Equity Grants (Detail) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Deferred Equity Units
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Beginning Balance, Units 329,757 439,193 310,469
Granted, Units    19,642 212,151
Vested, Units (150,398) (128,953) (83,607)
Forfeited, Units (4,066)      
Ending Balance, Units 175,298 329,757 439,193
Beginning Balance, Fair Value per unit $ 10.47 $ 8.00 $ 7.55
Granted, Fair Value per unit    $ 12.84 $ 8.00
Vested, Fair Value per unit $ (17.05) $ (12.84) $ (8.00)
Forfeited, Fair Value per unit $ (17.05)      
Ending Balance, Fair Value per unit   $ 10.47 $ 8.00
Deferred Equity Units | Minimum
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Ending Balance, Fair Value per unit $ 12.00    
Deferred Equity Units | Maximum
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Ending Balance, Fair Value per unit $ 17.05    
Performance Units
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Beginning Balance, Units 257,757 250,686 155,235
Granted, Units    9,821 106,076
Vested, Units         
Forfeited, Units (19,386) (2,750) (10,625)
Ending Balance, Units 238,371 257,757 250,686
Beginning Balance, Fair Value per unit $ 3.27 $ 3.07 $ 4.13
Granted, Fair Value per unit    $ 4.70 $ 3.07
Vested, Fair Value per unit       $ (3.07)
Forfeited, Fair Value per unit $ (3.75) $ (4.70)   
Ending Balance, Fair Value per unit $ 3.75 $ 3.27 $ 3.07