Income taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]

The components of loss before income taxes consist of the following:

	2017		2016		2015
Canadian	$	(14,841)	$	(13,602)	$	(11,574)
Foreign		(14,607)		(5,865)		(12,889)
Loss before income taxes	$	(29,448)	$	(19,467)	$	(24,473)

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

The reconciliation of income tax computed at statutory tax rates to income tax expense (recovery), using a 26.0% (2016 – 26.0%; 2015 – 26.0%) statutory tax rate, is:

	December 31, 2017			December 31, 2016			December 31, 2015
Loss before income taxes	$	(29,448)		$	(19,467)		$	(24,473)
Statutory tax rate		26.0	%		26.0	%		26.0	%
Income tax recovery at Canadian statutory income tax rates	$	(7,656)		$	(5,061)		$	(6,363)
Change in valuation allowance		1,625			4,197			4,290
Permanent differences		967			343			447
Expiry of investment tax credits		975			-			-
Tax rate differences		790			450			291
Change in U.S. statutory rate		6,394			-			-
Change in Canadian statutory rate		(2,595)			-			-
Other differences		(137)			223			1,324
Income tax expense (recovery)	$	363		$	152		$	(11)

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

Significant components of the Company’s deferred tax assets are shown below:

	December 31, 2017		December 31, 2016
Deferred tax assets:
Tax loss carryforwards	$	83,394	$	80,963
Research and development deductions and investment tax credits		27,168		27,709
Tax values of depreciable assets in excess of accounting values		3,008		3,230
Share issue costs and other		1,230		1,413
Total deferred tax assets		114,800		113,315
Valuation allowance		(114,480)		(112,855)
Net deferred tax assets	$	320	$	460

Investment Tax Credits and Non-Capital Losses [Table Text Block]

The Company’s Canadian federal and provincial investment tax credits and non-capital losses for income tax purposes expire as follows:

	Investment		Non-capital
	tax credits		losses
2018	$	145	$	35,932
2019		501		6,768
2020		481		17,991
2021		528		16,911
2022		296		23,129
Thereafter until 2037		13,586		255,879
	$	15,537	$	356,610