Employee Incentive Plans, Unrecognized Gross Compensation Cost Data Table (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2011 years
Service-based vested and non-vested common shares and restricted stock units [Member]
Unrecognized gross compensation cost data
Unrecognized gross compensation costs, by award type	$ 4.5
Expected period (in years) over which the remaining gross compensation costs will be recognized
Expected period (in years) over which the remaining gross compensation costs will be recognized, by award type	1.9
Performance Shares [Member]
Unrecognized gross compensation cost data
Unrecognized gross compensation costs, by award type	$ 4.7
Expected period (in years) over which the remaining gross compensation costs will be recognized
Expected period (in years) over which the remaining gross compensation costs will be recognized, by award type	2.2

The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph h

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration