Annual report pursuant to Section 13 and 15(d)

Share-based Compensation - Summary of Transactions for Non-Vested Stock Options (Detail)

v3.6.0.2
Share-based Compensation - Summary of Transactions for Non-Vested Stock Options (Detail) - $ / shares
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]      
Number of Shares, Non-vested options outstanding at beginning of period 176,688 379,106 391,625
Number of Shares, Options granted 0 28,000 158,000
Number of Shares, Options vested (130,223) (158,810) (139,602)
Number of Shares, Options forfeited (125) (71,608) (30,917)
Number of Shares, Non-vested options outstanding at end of period 46,340 176,688 379,106
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]      
Weighted-Average Exercise Price Per Share, Non-vested options outstanding at beginning of period (in usd per share) $ 19.13 $ 18.11 $ 15.56
Weighted-Average Exercise Price Per Share, Options granted (in usd per share) 0.00 23.47 21.30
Weighted-Average Exercise Price Per Share, Options vested (in usd per share) 17.83 16.80 15.34
Weighted-Average Exercise Price Per Share, Options forfeited (in usd per share) 144.00 20.59 14.64
Weighted-Average Exercise Price Per Share, Non-vested options outstanding at end of period (in usd per share) $ 22.42 $ 19.13 $ 18.11