Annual report pursuant to Section 13 and 15(d)

Cash, Cash Equivalents and Short-Term Investments - Schedule of Short-Term Investments (Details)

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Cash, Cash Equivalents and Short-Term Investments - Schedule of Short-Term Investments (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Cash And Cash Equivalents And Short Term Investments [Line Items]    
Short-term investments in continuous unrealized loss position for 12 months or less, Estimated fair value $ 3,399 $ 10,977
Short-term investments in continuous unrealized loss position for 12 months or less, Unrealized losses (2) (10)
US Treasury Securities    
Cash And Cash Equivalents And Short Term Investments [Line Items]    
Short-term investments in continuous unrealized loss position for 12 months or less, Estimated fair value 1,218 1,988
Short-term investments in continuous unrealized loss position for 12 months or less, Unrealized losses (1)  
Corporate Debt Securities    
Cash And Cash Equivalents And Short Term Investments [Line Items]    
Short-term investments in continuous unrealized loss position for 12 months or less, Estimated fair value 1,428 5,957
Short-term investments in continuous unrealized loss position for 12 months or less, Unrealized losses (1) (7)
Asset-backed Securities    
Cash And Cash Equivalents And Short Term Investments [Line Items]    
Short-term investments in continuous unrealized loss position for 12 months or less, Estimated fair value $ 753 3,032
Short-term investments in continuous unrealized loss position for 12 months or less, Unrealized losses   $ (3)