XML 115 R100.htm IDEA: XBRL DOCUMENT v3.10.0.1
Stock-based Compensation and Other Employee Benefits - Schedule of ESPP Purchase Rights and Underlying Weighted Average Assumptions (Detail) - ESPP purchase rights - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted average fair value per share $ 9.28 $ 12.09 $ 10.69
Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 37.00% 24.00% 22.00%
Risk-free interest rate 1.60% 0.70% 0.40%
Expected term (in years) 6 months 2 years 2 years
Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 107.00% 28.00% 32.00%
Risk-free interest rate 2.70% 1.30% 0.80%
Expected term (in years) 2 years 3 years 3 years