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Stock Plans - Summary of Performance Stock Unit Activity (Detail) - Performance Stock Unit Activity - $ / shares
3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]        
Unvested Shares, Beginning Balance 143,961 171,644 143,961 149,389
Granted, Shares   65,355 87,256 46,242
Vested, Shares   (31,181) (66,200) (91,696)
Performance adjustments, Shares   (15,594) 16,447 41,428
Forfeited, Shares (9,820) (3,603)   (1,402)
Unvested Shares, Ending Balance   186,621 171,644 143,961
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]        
Unvested Weighted Average Grant Date Fair Value, Beginning Balance (dollars per share) $ 52.42 $ 50.24 $ 52.42 $ 46.32
Granted, Weighted Average Grant Date Fair Value (dollars per share)   44.28 41.99 57.42
Vested, Weighted Average Grant Date Fair Value (dollars per share)   58.54 41.75 39.19
Performance adjustments, Weighted Average Grant Date Fair value (dollars per share)   58.54 41.45 39.42
Forfeited, Weighted Average Grant Date Fair Value (dollars per share) $ 51.51 44.47   48.85
Unvested Weighted Average Grant Date Fair Value, Ending Balance (dollars per share)   $ 46.18 $ 50.24 $ 52.42