Condensed Consolidated Interim Statements of Changes in Shareholders' Equity (unaudited) - USD ($) $ in Thousands	Total	Share Capital	Additional Paid-In Capital	Deficit	Total 4Front Ventures Corp. Shareholders' Equity	Non-Controlling Interest
Beginning Balance at Dec. 31, 2019	$ 74,760	$ 252,656	$ 25,618	$ (203,497)	$ 74,777	$ (17)
Beginning Balance, Shares at Dec. 31, 2019		531,522,819
GGP warrants issued with convertible debt	411		411		411
Conversion option on GGP notes transferred to equity	281		281		281
Share-based compensation	1,227		1,227		1,227
Net loss	(7,782)			(7,794)	(7,794)	12
Ending Balance at Mar. 31, 2020	68,897	$ 252,656	27,537	(211,291)	68,902	(5)
Ending Balance, Shares at Mar. 31, 2020		531,522,819
Beginning Balance at Dec. 31, 2020	42,203	$ 250,583	42,116	(250,548)	42,151	52
Beginning Balance, Shares at Dec. 31, 2020		538,851,252
Shares issued for Pure Ratios earnout	161	$ 161			161
Shares issued for Pure Ratios earnout, shares		473,491
Share-based compensation	2,396		2,396		2,396
Conversion of notes to equity	6,253	$ 6,253			6,253
Conversion of notes to equity, shares		24,366,003
Shares issued with exercise of stock options	$ 871	$ 871			871
Shares issued with exercise of stock options, shares	1,358,116	1,358,116
Shares issued with exercise of warrants	$ 1,563	$ 1,563			1,563
Shares issued with exercise of warrants, shares		2,422,363
Return of treasury shares		(8,320)
Net loss	(11,084)			(11,089)	(11,089)	5
Ending Balance at Mar. 31, 2021	$ 42,363	$ 259,431	$ 44,512	$ (261,637)	$ 42,306	$ 57
Ending Balance, Shares at Mar. 31, 2021	567,462,905	567,462,905