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Common Stock (Common Stock Rollfoward) (Details) - CAD CAD in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
Increase (Decrease) In Common Stock Shares [Roll Forward] |  |
Balance, January 1 | 147,210,000 | 143,780,000
Conversion of Convertible Debentures | 51,990,000 | 0
Issued for cash under Purchase Plans at market rate | 2,510,000 | 2,100,000
Discount on shares purchased under Dividend Reinvestment Plan | 0 | 0
Options exercised under senior management share option plan | 620,000 | 80,000
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period | 0 | 0
Balance, December 31 | 210,020,000 | 147,210,000
Increase (Decrease) In Common Stock Value [Roll Forward] |  |
Common Stock, Value, Issued, Beginning Balance | CAD 2,157,000 | CAD 2,016,000
Conversion of Convertible Debentures | 2,115,000 | 0
Issued for cash under Purchase Plans at market rate | 115,000 | 88,000
Discount on shares purchased under Dividend Reinvestment Plan Value | (5,000) | (4,000)
Options exercised under senior management share option plan | 17,000 | 2,000
Stock-based compensation | 1,000 | 1,000
Common Stock, Value, Issued, Ending Balance | CAD 4,738,000 | CAD 2,157,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum | 10.00% |
Employee Stock Option [Member] |  |
Increase (Decrease) In Common Stock Shares [Roll Forward] |  |
Options exercised under senior management share option plan | (622,168) |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Common Stock, Capital Shares Reserved for Future Issuance | 1,500,000 | 1,600,000
Stock Compensation Plan [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Common Stock, Capital Shares Reserved for Future Issuance | 6,600,000 | 7,300,000
Dividend Reinvestment [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Common Stock, Capital Shares Reserved for Future Issuance | 7,900,000 | 3,300,000

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