Stock Option Plans (Narrative) (Details)		6 Months Ended
Feb. 07, 2018 shares	Jun. 30, 2018 item shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock option plans \| item		2
Common shares issued upon exercise of options		1,300,000
2012 Equity Incentive Award Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares authorized for grant	4,600,000

Number of share options (or share units) exercised during the current period.

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