Annual report pursuant to Section 13 and 15(d)

Share-based Compensation - Summary of Stock Option Transactions under Plans (Detail)

v3.3.1.900
Share-based Compensation - Summary of Stock Option Transactions under Plans (Detail) - $ / shares
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]      
Number of Shares, options outstanding at beginning of period 603,872 546,595 342,950
Number of Shares, Options granted 28,000 158,000 305,000
Number of Shares, Options exercised (46,516) (37,569) (46,113)
Number of Shares, Options forfeited (71,608) (30,917) (36,566)
Number of Shares, Options expired (3,600) (32,237) (18,676)
Number of Shares, Options outstanding at end of period 510,148 603,872 546,595
Number of Shares, Options exercisable at end of period 333,460 224,766 154,970
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]      
Weighted-Average Exercise Price Per Share, Options outstanding at beginning of period (in usd per share) $ 23.78 $ 28.09 $ 37.44
Weighted-Average Exercise Price Per Share, Options granted (in usd per share) 23.47 21.30 16.43
Weighted-Average Exercise Price Per Share, Options exercised (in usd per share) 13.24 12.42 11.37
Weighted-Average Exercise Price Per Share, Options forfeited (in usd per share) 20.59 14.64 12.50
Weighted-Average Exercise Price Per Share, Options expired (in usd per share) 136.79 106.70 81.20
Weighted-Average Exercise Price Per Share, Options outstanding at end of period (in usd per share) 24.38 23.78 28.09
Weighted-Average Exercise Price Per Share, Options exercisable at end of period (in usd per share) $ 27.16 $ 33.35 $ 59.77