Annual report pursuant to Section 13 and 15(d)

Summary of Treasury Stock Activity (Parenthetical) (Detail)

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Summary of Treasury Stock Activity (Parenthetical) (Detail) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Schedule of Treasury Stock [Line Items]      
Common stock repurchased value as result of restricted stock forfeitures and canceled $ 0.001 $ 0.001 $ 0.001
Minimum      
Schedule of Treasury Stock [Line Items]      
Market Value of Restricted Shares 28.84 28.84 28.84
Maximum      
Schedule of Treasury Stock [Line Items]      
Market Value of Restricted Shares $ 44.67 $ 44.67 $ 44.67