Annual report pursuant to Section 13 and 15(d)

Stock Option and Purchase Plans - Summary of Weighted Average Fair Value of Options Granted (Detail)

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Stock Option and Purchase Plans - Summary of Weighted Average Fair Value of Options Granted (Detail) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Weighted average fair value of options granted (in usd per share) $ 20.70 $ 22.25 $ 16.83