Capital Stock (Details) - USD ($)		1 Months Ended					3 Months Ended		6 Months Ended
	Dec. 09, 2016	Jun. 30, 2018	Feb. 28, 2018	Jun. 30, 2017	Jan. 31, 2017	Dec. 31, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stock options
Stock-based compensation disclosure
Stock options granted to directors (in shares)									4,925,000
2001 Non-Employee Director Stock Plan
Stock-based compensation disclosure
Stock compensation expense (reduction)							$ 4,000	$ 21,000	$ 31,000	$ 32,000
2001 Non-Employee Director Stock Plan | Retiring director
Stock-based compensation disclosure
Stock compensation expense (reduction)		$ 72,000
Compensation Policy for Non-Employee Directors
Stock-based compensation disclosure
Stock compensation expense (reduction)							$ 54,000	$ 47,000	$ 156,000	$ 85,000
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			128,000
Compensation Policy for Non-Employee Directors | Deferred share units
Stock-based compensation disclosure
Common stock issued to retiring directors (in shares)		95,497	77,012		53,248
Vesting period	1 year