Annual report pursuant to Section 13 and 15(d)

Cash, Cash Equivalents and Investments - Cash Equivalents and Investments (Details)

v3.20.1
Cash, Cash Equivalents and Investments - Cash Equivalents and Investments (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amortized Cost $ 41,964 $ 53,379
Unrealized gains 57 4
Unrealized losses (127) (143)
Fair Value 41,894 53,240
US treasuries    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amortized Cost 5,293 7,541
Unrealized gains 25 0
Unrealized losses (18) (23)
Fair Value $ 5,300 $ 7,518
US treasuries | Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contractual maturity 46 days 150 days
US treasuries | Maximum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contractual maturity 182 days 164 days
Asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amortized Cost $ 7,962 $ 5,766
Unrealized gains 12 1
Unrealized losses (24) (9)
Fair Value $ 7,950 $ 5,758
Asset-backed securities | Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contractual maturity 49 days 196 days
Asset-backed securities | Maximum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contractual maturity 106 days 259 days
Asset-backed securities, greater than 365 | Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contractual maturity   365 days
Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amortized Cost $ 28,709 $ 40,072
Unrealized gains 20 3
Unrealized losses (85) (111)
Fair Value $ 28,644 $ 39,964
Corporate bonds | Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contractual maturity 2 days 73 days
Corporate bonds | Maximum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contractual maturity 204 days 252 days
Corporate bonds, greater than 365 | Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Contractual maturity   365 days