Common Shares - Summary Of Restricted Stock Units Activity (Details) - Restricted Stock Units (RSUs) - $ / shares	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested, Number of units, beginning of period (in shares)	1,002,670	1,567,907
Cancelled/forfeited, Number of units (in shares)	(198,821)	(246,683)
Vested, net of shares withheld, Number of units (in shares)	(142,380)	(637,554)
Granted, Number of units (in shares)		319,000
Unvested, Number of units, end of period (in shares)	661,469	1,002,670
Unvested, weighted average fair value, beginning of year (in dollars per share)	$ 0.78	$ 0.85
Cancelled/forfeited, Weighted average fair value (in dollars per share)	0.76	0.90
Vested, Weighted average fair value (in dollars per share)	0.75	0.88
Granted, Weighted average fair value (in dollars per share)		0.75
Unvested, weighted average fair value, end of year (in dollars per share)	$ 0.80	$ 0.78
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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