Share Incentive Plans (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]
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	8,595,553
Compensation information
Compensation Expense	$ 30,530	$ 34,607	$ 27,543
Compensation Capitalized	2,726	2,948	2,538
Restricted Units In-Lieu of Bonus (1)	4,022	3,654
Compensation Equity	37,278	41,209	30,081
Dividends Incurred	14,256	2,779	2,260
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 8,600
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 3 months 21 days
Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	14,725,321
Restricted Shares [Member]
Compensation information
Compensation Expense	$ 13,539	13,755	9,244
Compensation Capitalized	1,477	1,311	660
Restricted Units In-Lieu of Bonus (1)	0	0
Compensation Equity	15,016	15,066	9,904
Dividends Incurred	6,494	1,160	1,012
Restricted Stock Units (RSUs) [Member]
Compensation information
Compensation Expense	13,567	17,311	11,049
Compensation Capitalized	591	538	920
Restricted Units In-Lieu of Bonus (1)	4,022	3,654
Compensation Equity	18,180	21,503	11,969
Dividends Incurred	7,762	1,619	1,248
Employee Stock Option [Member]
Compensation information
Compensation Expense	2,839	2,746	6,453
Compensation Capitalized	593	1,010	896
Restricted Units In-Lieu of Bonus (1)	0	0
Compensation Equity	3,432	3,756	7,349
Dividends Incurred	0	0	0
Employee Share Purchase Plan Discount [Member]
Compensation information
Compensation Expense	585	795	797
Compensation Capitalized	65	89	62
Restricted Units In-Lieu of Bonus (1)	0	0
Compensation Equity	650	884	859
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
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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

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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.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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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.

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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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