Quarterly report pursuant to Section 13 or 15(d)

Summary of Share Activity Related to Restricted Stock Units (Detail)

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Summary of Share Activity Related to Restricted Stock Units (Detail) (Restricted Stock Units (RSUs), USD $)
3 Months Ended
Mar. 31, 2014
Restricted Stock Units (RSUs)
 
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Units, Nonvested, beginning of period 1,331,753
Units, Granted 1,150,233
Units, Vested   
Units, Forfeited (12,521)
Units, Nonvested, end of period 2,469,465
Weighted Average Grant Date Value Per Units, Beginning of period $ 14.96
Weighted Average Grant Date Fair Value Per Units, Granted $ 16.82
Weighted Average Grant Date Fair Value Per Units, Vested   
Weighted Average Grant Date Fair Value Per Units, Forfeited $ 15.10
Weighted Average Grant Date Value Per Units, End of period $ 15.82