XML 124 R102.htm IDEA: XBRL DOCUMENT v3.20.4
Stock-Based Compensation Expense - Schedule of Assumptions Used to Value Options Granted (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Employee stock purchase plan      
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]      
Expected life (in years) 2 years 2 years 2 years
Employee stock purchase plan | Minimum      
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]      
Risk-free interest rate 0.10% 1.70% 2.20%
Dividend yield 1.40% 3.50% 3.60%
Expected volatility 45.80% 51.70% 39.40%
Employee stock purchase plan | Maximum      
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]      
Risk-free interest rate 1.40% 2.50% 2.70%
Dividend yield 4.00% 5.40% 3.90%
Expected volatility 57.50% 53.40% 41.70%
Performance Stock Units      
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]      
Expected life (in years) 3 years    
Risk-free interest rate 0.20%    
Dividend yield 1.40%    
Expected volatility 51.30%