Common Shares (Details) - shares	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares issued	25,053,480	24,825,891
Shares outstanding	24,592,578	24,170,585
Exercisable at end of year (in shares)	747,500	932,500	1,116,750
Nil Coupon Perpetual Loan Notes
Number of shares reserved for future issuance	6,715
Reserved For Issuance Upon Exercise Or Vesting Of Equity Awards
Number of shares reserved for future issuance	25,053,480
Reserved For Issuance Upon Exercise Or Vesting Of Equity Awards \| Stock options
Number of shares reserved for future issuance	5,600,676

Aggregate number of common shares reserved for future issuance.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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-Publisher FASB
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-SubTopic 10
-Section 50
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