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401(k) Plan (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Retirement Benefits [Abstract]      
Employer matching contribution, percent 50.00%    
Maximum annual contribution per employee, percent 6.00%    
Company's contribution to 401(k) plan $ 1,200 $ 822 $ 496