Capital Management - Additional Information (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Capital Management [Line Items]
Shareholders’ equity	$ 42,363	$ 42,203	$ 68,897	$ 74,760
Total 4Front Ventures Corp. Shareholders' Equity
Capital Management [Line Items]
Shareholders’ equity	$ 42,306	$ 42,151	$ 68,902	$ 74,777