Share Incentive and Other Compensation - Employee Share Purchase Plan and Deferred Share Plan (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee share purchase discount rate (in percent)	15.00%
Employee share purchase maximum purchase amount	$ 25
Trustee [Member] \| Deferred Compensation [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation arrangement compensation expense	$ 100	$ 100	$ 100
Common Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee share purchase (in shares)	3,491	3,761	4,668

Employee Stock Ownership Plan, Allowable Share Purchase Amount Per Annum, Maximum

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- Definition

Employee Stock Ownership Plan, Purchase Discount Rate

+ References

No definition available.

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- Definition

The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 30
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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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