Annual report pursuant to Section 13 and 15(d)

Summary of Restricted Stock Activity (Detail)

v3.6.0.2
Summary of Restricted Stock Activity (Detail) - Restricted Stock - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Shares of Restricted Stock      
Shares of Restricted Stock, Beginning balance 757,775 878,897 1,260,913
Shares of Restricted Stock, Granted 335,707 226,212 269,774
Shares of Restricted Stock, Vested (430,056) (329,437) (625,843)
Shares of Restricted Stock, Forfeited (56,808) (17,897) (25,947)
Shares of Restricted Stock, Ending balance 606,618 757,775 878,897
Weighted Average Grant Date Fair Value      
Weighted Average Grant Date Fair Value Outstanding, Beginning $ 30.73 $ 24.92 $ 21.86
Weighted Average Grant Date Fair Value, Granted 30.98 42.79 28.93
Weighted Average Grant Date Fair Value, Vested 26.60 23.72 20.53
Weighted Average Grant Date Fair Value, Forfeited 33.81 27.58 22.94
Weighted Average Grant Date Fair Value Outstanding, Ending $ 33.51 $ 30.73 $ 24.92