Condensed Consolidated Statements of Shareholders’ Equity (Deficit) and Convertible Preferred Shares - USD ($) $ in Thousands	Common shares	Class A1 preferred shares	Class A2 preferred shares	Class B preferred shares	Class C preferred shares	Class D1 preferred shares	Class D2 preferred shares	Additional paid-in capital	Cumulative translation adjustment	Accumulated deficit	Total
Balance at the beginning of period at Dec. 31, 2017	$ 1,228							$ 2,372	$ (1,634)	$ (35,085)
Balance at the beginning of period (in shares) at Dec. 31, 2017	239,990
Temporary equity, balance at the beginning of period at Dec. 31, 2017		$ 2,027	$ 12,643	$ 17,195	$ 27,236	$ 0	$ 0
Temporary equity, balance at the beginning of period (in shares) at Dec. 31, 2017		372,211	2,443,914	2,830,907	3,786,878	0	0
Total Equity, Balance at the beginning of period at Dec. 31, 2017											$ 25,985
Increase (Decrease) in Stockholders' Equity and Temporary Equity [Roll Forward]
Net loss and comprehensive loss										(4,181)	(4,181)
Exercise of stock options (note 5)	$ 55							(25)			30
Exercise of stock options (note 5) (in shares)	37,675
Share-based compensation (note 5)								125			125
Balance at the end of period at Mar. 31, 2018	$ 1,283							2,472	(1,634)	(39,266)
Balance at the end of period (in shares) at Mar. 31, 2018	277,665
Temporary equity, balance at the end of period at Mar. 31, 2018		$ 2,027	$ 12,643	$ 17,195	$ 27,236
Temporary equity, balance at the end of period (in shares) at Mar. 31, 2018		372,211	2,443,914	2,830,907	3,786,878
Total Equity, Balance at the end of period at Mar. 31, 2018											21,959
Balance at the beginning of period at Dec. 31, 2017	$ 1,228							2,372	(1,634)	(35,085)
Balance at the beginning of period (in shares) at Dec. 31, 2017	239,990
Temporary equity, balance at the beginning of period at Dec. 31, 2017		$ 2,027	$ 12,643	$ 17,195	$ 27,236	$ 0	$ 0
Temporary equity, balance at the beginning of period (in shares) at Dec. 31, 2017		372,211	2,443,914	2,830,907	3,786,878	0	0
Total Equity, Balance at the beginning of period at Dec. 31, 2017											25,985
Increase (Decrease) in Stockholders' Equity and Temporary Equity [Roll Forward]
Net loss and comprehensive loss											$ (13,468)
Exercise of stock options (note 5)								(32)
Exercise of stock options (note 5) (in shares)											42,781
Share-based compensation (note 5)								289
Balance at the end of period at Sep. 30, 2018	$ 1,297							2,629	(1,634)	(48,555)
Balance at the end of period (in shares) at Sep. 30, 2018	282,771
Temporary equity, balance at the end of period at Sep. 30, 2018		$ 2,027	$ 12,643	$ 17,195	$ 27,236
Temporary equity, balance at the end of period (in shares) at Sep. 30, 2018		372,211	2,443,914	2,830,907	3,786,878
Total Equity, Balance at the end of period at Sep. 30, 2018											$ 12,841
Balance at the beginning of period at Mar. 31, 2018	$ 1,283							2,472	(1,634)	(39,266)
Balance at the beginning of period (in shares) at Mar. 31, 2018	277,665
Temporary equity, balance at the beginning of period at Mar. 31, 2018		$ 2,027	$ 12,643	$ 17,195	$ 27,236
Temporary equity, balance at the beginning of period (in shares) at Mar. 31, 2018		372,211	2,443,914	2,830,907	3,786,878
Total Equity, Balance at the beginning of period at Mar. 31, 2018											21,959
Increase (Decrease) in Stockholders' Equity and Temporary Equity [Roll Forward]
Net loss and comprehensive loss										(3,589)	(3,589)
Exercise of stock options (note 5)	$ 14							(7)			7
Exercise of stock options (note 5) (in shares)	5,106
Share-based compensation (note 5)								79			79
Balance at the end of period at Jun. 30, 2018	$ 1,297							2,544	(1,634)	(42,855)
Balance at the end of period (in shares) at Jun. 30, 2018	282,771
Temporary equity, balance at the end of period at Jun. 30, 2018		$ 2,027	$ 12,643	$ 17,195	$ 27,236
Temporary equity, balance at the end of period (in shares) at Jun. 30, 2018		372,211	2,443,914	2,830,907	3,786,878
Total Equity, Balance at the end of period at Jun. 30, 2018											18,456
Increase (Decrease) in Stockholders' Equity and Temporary Equity [Roll Forward]
Net loss and comprehensive loss										(5,700)	(5,700)
Share-based compensation (note 5)								85			85
Balance at the end of period at Sep. 30, 2018	$ 1,297							2,629	(1,634)	(48,555)
Balance at the end of period (in shares) at Sep. 30, 2018	282,771
Temporary equity, balance at the end of period at Sep. 30, 2018		$ 2,027	$ 12,643	$ 17,195	$ 27,236
Temporary equity, balance at the end of period (in shares) at Sep. 30, 2018		372,211	2,443,914	2,830,907	3,786,878
Total Equity, Balance at the end of period at Sep. 30, 2018											12,841
Balance at the beginning of period at Dec. 31, 2018	$ 2,039							2,655	(1,634)	(58,270)	$ (55,210)
Balance at the beginning of period (in shares) at Dec. 31, 2018	596,787										596,787
Temporary equity, balance at the beginning of period at Dec. 31, 2018		$ 2,027	$ 12,643	$ 17,198	$ 27,236	$ 64,719	$ 14,935				$ 138,758
Temporary equity, balance at the beginning of period (in shares) at Dec. 31, 2018		372,211	2,443,914	2,830,907	3,786,878	6,893,236	1,223,656
Total Equity, Balance at the beginning of period at Dec. 31, 2018											83,548
Increase (Decrease) in Stockholders' Equity and Temporary Equity [Roll Forward]
Net loss and comprehensive loss										(10,452)	(10,452)
Exercise of stock options (note 5)	$ 51							(26)			25
Exercise of stock options (note 5) (in shares)	18,153
Share-based compensation (note 5)								211			211
Balance at the end of period at Mar. 31, 2019	$ 2,090							2,840	(1,634)	(68,722)
Balance at the end of period (in shares) at Mar. 31, 2019	614,940
Temporary equity, balance at the end of period at Mar. 31, 2019		$ 2,027	$ 12,643	$ 17,198	$ 27,236	$ 64,719	$ 14,935
Temporary equity, balance at the end of period (in shares) at Mar. 31, 2019		372,211	2,443,914	2,830,907	3,786,878	6,893,236	1,223,656
Total Equity, Balance at the end of period at Mar. 31, 2019											73,332
Balance at the beginning of period at Dec. 31, 2018	$ 2,039							2,655	(1,634)	(58,270)	$ (55,210)
Balance at the beginning of period (in shares) at Dec. 31, 2018	596,787										596,787
Temporary equity, balance at the beginning of period at Dec. 31, 2018		$ 2,027	$ 12,643	$ 17,198	$ 27,236	$ 64,719	$ 14,935				$ 138,758
Temporary equity, balance at the beginning of period (in shares) at Dec. 31, 2018		372,211	2,443,914	2,830,907	3,786,878	6,893,236	1,223,656
Total Equity, Balance at the beginning of period at Dec. 31, 2018											83,548
Increase (Decrease) in Stockholders' Equity and Temporary Equity [Roll Forward]
Net loss and comprehensive loss											$ (36,941)
Exercise of stock options (note 5)								(26)
Exercise of stock options (note 5) (in shares)											18,153
Share-based compensation (note 5)								837
Balance at the end of period at Sep. 30, 2019	$ 226,211							3,466	(1,634)	(95,211)	$ 132,832
Balance at the end of period (in shares) at Sep. 30, 2019	24,490,742										24,490,742
Temporary equity, balance at the end of period at Sep. 30, 2019		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Temporary equity, balance at the end of period (in shares) at Sep. 30, 2019		0	0	0	0	0	0
Total Equity, Balance at the end of period at Sep. 30, 2019											$ 132,832
Balance at the beginning of period at Mar. 31, 2019	$ 2,090							2,840	(1,634)	(68,722)
Balance at the beginning of period (in shares) at Mar. 31, 2019	614,940
Temporary equity, balance at the beginning of period at Mar. 31, 2019		$ 2,027	$ 12,643	$ 17,198	$ 27,236	$ 64,719	$ 14,935
Temporary equity, balance at the beginning of period (in shares) at Mar. 31, 2019		372,211	2,443,914	2,830,907	3,786,878	6,893,236	1,223,656
Total Equity, Balance at the beginning of period at Mar. 31, 2019											73,332
Increase (Decrease) in Stockholders' Equity and Temporary Equity [Roll Forward]
Net loss and comprehensive loss										(13,658)	(13,658)
Share-based compensation (note 5)								276			276
Initial public offering (note 5)	$ 85,363										85,363
Initial public offering (note 5) (in shares)	6,325,000
Preferred share conversion (note 5)	$ 138,758
Preferred share conversion (note 5) (in shares)	17,550,802
Balance at the end of period at Jun. 30, 2019	$ 226,211							3,116	(1,634)	(82,380)
Balance at the end of period (in shares) at Jun. 30, 2019	24,490,742
Temporary equity, balance at the end of period at Jun. 30, 2019		$ (2,027)	$ (12,643)	$ (17,198)	$ (27,236)	$ (64,719)	$ (14,935)
Temporary equity, balance at the end of period (in shares) at Jun. 30, 2019		(372,211)	(2,443,914)	(2,830,907)	(3,786,878)	(6,893,236)	(1,223,656)
Total Equity, Balance at the end of period at Jun. 30, 2019											145,313
Increase (Decrease) in Stockholders' Equity and Temporary Equity [Roll Forward]
Net loss and comprehensive loss										(12,831)	(12,831)
Share-based compensation (note 5)								350			350
Balance at the end of period at Sep. 30, 2019	$ 226,211							$ 3,466	$ (1,634)	$ (95,211)	$ 132,832
Balance at the end of period (in shares) at Sep. 30, 2019	24,490,742										24,490,742
Temporary equity, balance at the end of period at Sep. 30, 2019		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Temporary equity, balance at the end of period (in shares) at Sep. 30, 2019		0	0	0	0	0	0
Total Equity, Balance at the end of period at Sep. 30, 2019											$ 132,832