XML 88 R73.htm IDEA: XBRL DOCUMENT v3.19.1
Employee Benefit Plans and Stock-Based Compensation - Assumptions (Details) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Weighted-average assumptions [Abstract]      
Expected term 5 years 9 months 18 days 5 years 9 months 18 days 4 years
Volatility (in hundredths) 46.60% 46.50% 46.50%
Risk-free interest rate (in hundredths) 3.09% 2.10% 1.47%
Retirement Savings Plan [Abstract]      
Period after which all full time employees are eligible to participate in the savings plan 90 days    
Contributions to the retirement savings plans $ 180,000 $ 149,000 $ 133,000
Maximum      
Retirement Savings Plan [Abstract]      
Maximum percentage of employer matching contribution if employees contribute at least 6% of base pay (in hundredths) 4.00%    
Minimum      
Retirement Savings Plan [Abstract]      
Minimum percentage of employee contribution to get 4% of employer's contribution (in hundredths) 6.00%