Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Summary of Fair Value Assets Measured on Recurring Basis for Cash, Cash Equivalents and Marketable Securities (Details)

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Summary of Significant Accounting Policies - Summary of Fair Value Assets Measured on Recurring Basis for Cash, Cash Equivalents and Marketable Securities (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cash and cash equivalents $ 198,037 $ 196,634
Fair Value Measurements Recurring    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Adjusted cost 209,086 240,358
Gross unrealized gains (losses) 8 (9)
Fair value 209,094 240,349
Cash and cash equivalents 198,037 196,634
Marketable securities 11,057 43,715
Fair Value Measurements Recurring | Cash    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Adjusted cost 51,560 33,671
Fair value 51,560 33,671
Cash and cash equivalents 51,560 33,671
Fair Value Measurements Recurring | Level 1 | Money Market Accounts    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Adjusted cost 146,477 158,438
Fair value 146,477 158,438
Cash and cash equivalents 146,477 158,438
Fair Value Measurements Recurring | Level 2 | Corporate Bonds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Adjusted cost 2,011 13,629
Gross unrealized gains (losses) 2 (16)
Fair value 2,013 13,613
Marketable securities 2,013 13,613
Fair Value Measurements Recurring | Level 2 | U.S. Treasury Securities    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Adjusted cost 9,038 34,620
Gross unrealized gains (losses) 6 7
Fair value 9,044 34,627
Cash and cash equivalents   4,525
Marketable securities $ 9,044 $ 30,102