INCOME TAXES (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) ongoing_tax_audit	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Net loss before tax	$ (98,418,000)	$ (70,430,000)	$ (83,118,000)
Statutory combined US federal and state tax rate (2012 - statutory combined Canadian federal and provincial tax rate)	21.00%	34.00%	34.00%
Statutory federal and provincial taxes	$ (20,668,000)	$ (23,946,000)	$ (28,260,000)
Effect of change in valuation allowance	25,959,000	(4,154,000)	28,446,000
Non-deductible share-based compensation	884,000	695,000	1,247,000
Tax deductions for share-based compensation	(2,924,000)	(80,000)	(12,000)
Tax credits	(5,130,000)	(2,563,000)	(2,906,000)
Share issue costs - temporary difference	0	0	(78,000)
Write off of Methylgene US Inc. net operating loss	0	307,000	0
Differential in income tax rates of foreign subsidiary	(1,000)	(169,000)	261,000
Change in tax rate	0	303,000	0
Tax Cuts and Jobs Act	0	28,569,000	0
Uncertain tax positions	1,283,000	646,000	3,921,000
Return to provision and other true-ups	375,000	394,000	(2,619,000)
Other differences	222,000	(2,000)	0
Income tax expense (benefit)	0	0	0
Deferred tax asset
Tangible and intangible depreciable assets	8,123,000	17,927,000
Stock compensation	6,515,000	4,976,000
Provisions	1,020,000	611,000
Net operating loss carry forwards	74,721,000	44,598,000
Capital loss carryforward	178,000	83,000
Canada scientific research and experimental development expenditures	5,467,000	5,467,000
U.S. research and development tax credits	10,613,000	7,016,000
Total gross deferred tax assets	106,637,000	80,678,000
Less valuation allowance	(106,637,000)	(80,678,000)
Net deferred tax assets	0	0
Additional disclosures
Amount of increase in valuation allowance	(26,000,000)
Reconciliation of the beginning and ending gross amounts of unrecognized tax positions
Accrual for interest or penalties on tax matters	$ 0
Number of ongoing tax audits | ongoing_tax_audit	0
Deferred tax asset, provisional income tax expense related to the TCJA		28,600,000
Domestic Tax Authority
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense (benefit)	$ 0	0	0
Canadian Federal
Additional disclosures
Scientific research and experimental development expenses deductible for income tax purposes	19,900,000	19,900,000
Net operating loss carry forwards (NOLs)	79,863,000
Reconciliation of the beginning and ending gross amounts of unrecognized tax positions
Unrecognized tax positions, beginning of year	1,693,000	1,095,000	509,000
Gross increase — current period tax positions	924,000	588,000	598,000
Gross decrease — prior period tax positions	0	0	(9,000)
Gross increase — prior period tax positions	0	11,000	0
Expiration of statute of limitations	0	(1,000)	(3,000)
Unrecognized tax positions, end of year	2,617,000	1,693,000	1,095,000
Canadian Federal | 2030
Additional disclosures
Net operating loss carry forwards (NOLs)	5,907,000
Canadian Federal | 2031
Additional disclosures
Net operating loss carry forwards (NOLs)	7,059,000
Canadian Federal | 2032
Additional disclosures
Net operating loss carry forwards (NOLs)	13,308,000
Canadian Federal | 2033
Additional disclosures
Net operating loss carry forwards (NOLs)	18,623,000
Canadian Federal | 2034
Additional disclosures
Net operating loss carry forwards (NOLs)	32,401,000
Canadian Federal | 2035
Additional disclosures
Net operating loss carry forwards (NOLs)	1,084,000
Canadian Federal | 2036
Additional disclosures
Net operating loss carry forwards (NOLs)	777,000
Canadian Federal | 2037
Additional disclosures
Net operating loss carry forwards (NOLs)	697,000
Canadian Federal | 2038
Additional disclosures
Net operating loss carry forwards (NOLs)	7,000
Canadian Federal | Does not expire
Additional disclosures
Net operating loss carry forwards (NOLs)	0
Canadian Provincial
Additional disclosures
Scientific research and experimental development expenses deductible for income tax purposes	21,600,000	21,600,000
Net operating loss carry forwards (NOLs)	79,243,000
Reconciliation of the beginning and ending gross amounts of unrecognized tax positions
Unrecognized tax positions, beginning of year	7,556,000	7,333,000	2,274,000
Gross increase — current period tax positions	454,000	227,000	195,000
Gross decrease — prior period tax positions	0	(3,000)	0
Gross increase — prior period tax positions	0	0	4,866,000
Expiration of statute of limitations	0	(1,000)	(2,000)
Unrecognized tax positions, end of year	8,010,000	$ 7,556,000	$ 7,333,000
Canadian Provincial | 2030
Additional disclosures
Net operating loss carry forwards (NOLs)	5,985,000
Canadian Provincial | 2031
Additional disclosures
Net operating loss carry forwards (NOLs)	7,066,000
Canadian Provincial | 2032
Additional disclosures
Net operating loss carry forwards (NOLs)	12,433,000
Canadian Provincial | 2033
Additional disclosures
Net operating loss carry forwards (NOLs)	19,385,000
Canadian Provincial | 2034
Additional disclosures
Net operating loss carry forwards (NOLs)	31,809,000
Canadian Provincial | 2035
Additional disclosures
Net operating loss carry forwards (NOLs)	1,084,000
Canadian Provincial | 2036
Additional disclosures
Net operating loss carry forwards (NOLs)	777,000
Canadian Provincial | 2037
Additional disclosures
Net operating loss carry forwards (NOLs)	697,000
Canadian Provincial | 2038
Additional disclosures
Net operating loss carry forwards (NOLs)	7,000
Canadian Provincial | Does not expire
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US Federal
Additional disclosures
Net operating loss carry forwards (NOLs)	254,611,000
US Federal | 2030
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US Federal | 2031
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US Federal | 2032
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US Federal | 2033
Additional disclosures
Net operating loss carry forwards (NOLs)	2,225,000
US Federal | 2034
Additional disclosures
Net operating loss carry forwards (NOLs)	7,276,000
US Federal | 2035
Additional disclosures
Net operating loss carry forwards (NOLs)	53,359,000
US Federal | 2036
Additional disclosures
Net operating loss carry forwards (NOLs)	23,379,000
US Federal | 2037
Additional disclosures
Net operating loss carry forwards (NOLs)	65,509,000
US Federal | 2038
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US Federal | Does not expire
Additional disclosures
Net operating loss carry forwards (NOLs)	102,863,000
US Federal | Research Tax Credit Carryforward
Additional disclosures
Tax credit carryforward	10,600,000
US State
Additional disclosures
Net operating loss carry forwards (NOLs)	77,344,000
US State | 2030
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State | 2031
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State | 2032
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State | 2033
Additional disclosures
Net operating loss carry forwards (NOLs)	2,232,000
US State | 2034
Additional disclosures
Net operating loss carry forwards (NOLs)	22,162,000
US State | 2035
Additional disclosures
Net operating loss carry forwards (NOLs)	52,950,000
US State | 2036
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State | 2037
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State | 2038
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State | Does not expire
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State | Research Tax Credit Carryforward
Additional disclosures
Tax credit carryforward	$ 4,700,000