XML 90 R79.htm IDEA: XBRL DOCUMENT v3.4.0.3
Stock-Based Compensation - Significant Assumptions Used to Estimate Fair Value of Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan
3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected dividends 0.00% 0.00%
Expected volatility, maximum 34.97% 30.73%
Risk-free interest rate, maximum 0.81% 0.49%
Expected volatility, minimum 31.85% 30.04%
Risk-free interest rate, minimum 0.47% 0.07%
Maximum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected life (years) 2 years 2 years
Minimum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected life (years) 6 months 6 months