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Share-Based Compensation and Employee Benefit Plans (Details 5) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Performance share units |  |  |
Share-Based Compensation |  |  |
Estimated pre-vesting forfeitures (as a percent) | 0.00% | 0.00% |
Unrecognized compensation cost | 2.9 |  |
Expected weighted average period during which unrecognized compensation cost will be recognized (in years) | 2 |  |
Restricted shares |  |  |
Share-Based Compensation |  |  |
Unrecognized compensation cost | 12.5 |  |
Expected weighted average period during which unrecognized compensation cost will be recognized (in years) | 2 |  |
Restricted shares | Minimum |  |  |
Share-Based Compensation |  |  |
Estimated pre-vesting forfeitures (as a percent) | 0.00% | 0.00% | 2.00%
Restricted shares | Maximum |  |  |
Share-Based Compensation |  |  |
Estimated pre-vesting forfeitures (as a percent) | 4.00% | 4.00% | 5.00%
Options |  |  |
Share-Based Compensation |  |  |
Estimated pre-vesting forfeitures (as a percent) |  |  | 0.00%

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- Definition Represents the estimated pre-vesting percentage of forfeitures considered for reduction in stock compensation expense recognized during the period. + References No definition available. + Details
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- Definition As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest. + References 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of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph h -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 + Details
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- Definition 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. + References 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 + Details
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