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Commitments and Contingencies (Narrative) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]      
401(k) plan, minimum eligibility age 18 years    
401(k) plan, requisite service period 6 months    
401(k) plan, maximum annual contribution per employee, percent 100.00%    
401(k) plan, employer's matching contribution, annual vesting percentage 20.00%    
401(k) plan, employer contribution, ultimate vesting percentage 100.00%    
401(k) plan, employer's matching contribution, vesting term 6 years    
401(k) plan, employer contribution amount $ 355 $ 301 $ 295
Operating leases, maximum term 5 years    
Operating leases, rent expense $ 433 $ 310 $ 325