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Derivative Financial Instruments - Narrative (Details) - Marketwise, LLC
$ in Thousands
12 Months Ended
Dec. 31, 2020
USD ($)
instrument
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Derivative [Line Items]      
Cash received upon issuance of derivative instruments | $ $ 0 $ 0 $ 306
Number of derivative instruments outstanding (instrument) | instrument 1