Annual report pursuant to Section 13 and 15(d)

Cash, Cash Equivalents and Investments - Cash Equivalents and Investments Carried at Fair Value (Details)

v3.19.1
Cash, Cash Equivalents and Investments - Cash Equivalents and Investments Carried at Fair Value (Details) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds, included in cash equivalents $ 7,791 $ 4,583
Corporate bonds, included in cash equivalents 10,910 13,595
Investments - US treasuries 7,518 4,172
Investments - Asset-backed securities 5,758 6,384
Investments - Corporate bonds 39,964 34,117
Total 71,941 62,851
Quoted prices in active markets (Level 1)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds, included in cash equivalents 7,791 4,583
Corporate bonds, included in cash equivalents 0 0
Investments - US treasuries 7,518 4,172
Investments - Asset-backed securities 0 0
Investments - Corporate bonds 0 0
Total 15,309 8,755
Significant other observable inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds, included in cash equivalents 0 0
Corporate bonds, included in cash equivalents 10,910 13,595
Investments - US treasuries 0 0
Investments - Asset-backed securities 5,758 6,384
Investments - Corporate bonds 39,964 34,117
Total 56,632 54,096
Significant unobservable inputs (Level 3)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money market funds, included in cash equivalents 0 0
Corporate bonds, included in cash equivalents 0 0
Investments - US treasuries 0 0
Investments - Asset-backed securities 0 0
Investments - Corporate bonds 0 0
Total $ 0 $ 0