Share Incentive Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Compensation information
Compensation Expense	$ 21,177	$ 18,875	$ 17,843
Compensation Capitalized	2,305	2,141	1,961
Compensation Equity	23,482	21,016	19,804
Dividends Incurred	1,320	1,472	1,881
Performance Shares [Member]
Compensation information
Compensation Expense			103
Compensation Capitalized			76
Compensation Equity			179
Dividends Incurred			0
Restricted shares [Member]
Compensation information
Compensation Expense	8,041	8,603	10,065
Compensation Capitalized	1,061	1,178	1,067
Compensation Equity	9,102	9,781	11,132
Dividends Incurred	1,121	1,334	1,627
Long Term Investment Plan Units [Member]
Compensation information
Compensation Expense	3,344	2,334	1,036
Compensation Capitalized	297	190	158
Compensation Equity	3,641	2,524	1,194
Dividends Incurred	199	138	254
Employee Stock Option [Member]
Compensation information
Compensation Expense	8,711	6,707	5,458
Compensation Capitalized	834	714	538
Compensation Equity	9,545	7,421	5,996
Dividends Incurred	0	0	0
ESPP Discount [Member]
Compensation information
Compensation Expense	1,081	1,231	1,181
Compensation Capitalized	113	59	122
Compensation Equity	1,194	1,290	1,303
Dividends Incurred	$ 0	$ 0	$ 0

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".

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 35

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A91

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 20

-Section 55

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=6576910&loc=d3e11178-113907

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 39

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- 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+ Details