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Cash Equivalents and Investments (Tables)
6 Months Ended
Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]  
Schedule of Investments
                                 
 
June 30, 2019
   
December 31, 2018
 
 
Short-Term
   
Long-Term
   
Short-Term
   
Long-Term
 
Municipal debt securities
  $
43,272
    $
—  
    $
18,473
    $
30,841
 
Federal home loan securities
   
34,397
     
—  
     
2,000
     
34,393
 
Certificates of deposit
   
5,166
     
—  
     
1,450
     
4,465
 
                                 
  $
82,835
    $
—  
    $
21,923
    $
69,699