Common Shares - Warrants (Details) - Warrants - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)	6,514,625	6,514,625	6,514,625
Weighted average exercise price of warrants outstanding (in dollars per share)	$ 1.92	$ 1.92	$ 1.92
Weighted average remaining life, warrants outstanding	7 months 6 days	1 year 7 months 6 days	2 years 7 months 6 days