Share Incentive and Other Compensation - Employee Share Purchase Plan and Deferred Share Plan - Additional Information (Details) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee share purchase discount rate	15.00%
Employee share purchase maximum purchase amount	$ 25,000
Common Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee share purchase (in shares)	706	943

Employee stock ownership plan allowable share purchase amount per annum maximum.

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- Definition

Discount rate from fair value on purchase date that participants pay for shares.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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