Capital Stock (Details) - USD ($)		1 Months Ended					3 Months Ended
	Dec. 09, 2016	Feb. 28, 2018	Jun. 30, 2017	Jan. 31, 2017	Dec. 31, 2016	Jun. 30, 2004	Mar. 31, 2018	Mar. 31, 2017
Stock-based compensation disclosure
Stock compensation expense (reduction)							$ 3,700,000	$ 2,600,000
Stock options
Stock-based compensation disclosure
Stock options granted to directors (in shares)							4,465,000
2001 Director Plan
Stock-based compensation disclosure
Stock compensation expense (reduction)							$ 26,000	12,000
Stock units issued (in shares)						0
Compensation Policy for Non-Employee Directors
Stock-based compensation disclosure
Stock compensation expense (reduction)							$ 102,000	$ 38,000
Compensation Policy for Non-Employee Directors | Stock options
Stock-based compensation disclosure
Vesting period							1 year
Stock options granted to directors (in shares)			80,000		40,000
Compensation Policy for Non-Employee Directors | Deferred share units
Stock-based compensation disclosure
Stock units issued (in shares)		77,012		53,248
Vesting period	1 year