Annual report pursuant to Section 13 and 15(d)

Summary of Treasury Stock Activity (Parenthetical) (Detail)

v3.6.0.2
Summary of Treasury Stock Activity (Parenthetical) (Detail) - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
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 29.17 29.17 29.17
Maximum      
Schedule of Treasury Stock [Line Items]      
Market Value of Restricted Shares $ 39.20 $ 39.20 $ 39.20