CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Other comprehensive income (loss), tax	$ 0	$ 0	$ 0	$ 0
Changes in fair value of available-for-sale securities	$ 4	$ 0	$ (16)	$ 0

Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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+ Details