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Cash and Marketable Securities - Reconciliation of Cash and Cash Equivalents (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Cash and Cash Equivalents [Abstract]        
Cash and cash equivalents $ 309,324 $ 134,669 $ 32,191 $ 38,223
Restricted cash 269 270 242 256
Total cash, cash equivalents, and restricted cash at the end of the period $ 309,593 $ 134,939 $ 32,433 $ 38,479