Annual report pursuant to Section 13 and 15(d)

Stock Option and Purchase Plans - Fair Value for Options Granted under Employee Stock Purchase Plan (Detail)

v3.3.1.900
Stock Option and Purchase Plans - Fair Value for Options Granted under Employee Stock Purchase Plan (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]      
Dividend yield 0.00% 0.00% 0.00%
Employee Stock      
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]      
Risk-free interest rate 0.31% 0.10% 0.10%
Dividend yield 0.00% 0.00% 0.00%
Volatility factor 0.40% 0.42% 0.37%
Expected life in years 1 year 1 year 1 year