Share Incentive Plans (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	12,980,741
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	7,952,498
Compensation information
Compensation Expense	$ 34,607	$ 27,543	$ 35,474
Compensation Capitalized	2,948	2,538	2,545
Restricted Units In-Lieu of Bonus (1)	3,654
Compensation Equity	41,209	30,081	38,019
Dividends Incurred	2,779	2,260	1,487
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 10,600
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 3 months 21 days
Restricted Shares [Member]
Compensation information
Compensation Expense	$ 13,755	9,244	12,185
Compensation Capitalized	1,311	660	1,079
Restricted Units In-Lieu of Bonus (1)	0
Compensation Equity	15,066	9,904	13,264
Dividends Incurred	1,160	1,012	967
Restricted Stock Units (RSUs) [Member]
Compensation information
Compensation Expense	17,311	11,049	13,108
Compensation Capitalized	538	920	501
Restricted Units In-Lieu of Bonus (1)	3,654
Compensation Equity	21,503	11,969	13,609
Dividends Incurred	1,619	1,248	520
Employee Stock Option [Member]
Compensation information
Compensation Expense	2,746	6,453	9,569
Compensation Capitalized	1,010	896	945
Restricted Units In-Lieu of Bonus (1)	0
Compensation Equity	3,756	7,349	10,514
Dividends Incurred	0	0	0
Employee Share Purchase Plan Discount [Member]
Compensation information
Compensation Expense	795	797	612
Compensation Capitalized	89	62	20
Restricted Units In-Lieu of Bonus (1)	0
Compensation Equity	884	859	632
Dividends Incurred	$ 0	$ 0	$ 0

Share based compensation expense related Disclosure

No definition available.

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- Definition

Represents dividends paid during the period for each type of long term compensation outstanding.

+ References

No definition available.

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- Definition

This element represents the amount of recognized equity-based compensation during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Alternate captions include the words "stock-based compensation".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14
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- Definition

Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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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

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

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- Definition

Value of stock issued in lieu of cash for services contributed to the entity. Value of the stock issued includes, but is not limited to, services contributed by vendors and founders.

+ References

No definition available.

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