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Employee Share-Based Incentive Compensation Plans (Details 3) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009 | Jun. 30, 2011 WTM Restricted Stock | Mar. 31, 2011 WTM Restricted Stock | Dec. 31, 2011 WTM Restricted Stock | Dec. 31, 2010 WTM Restricted Stock | Dec. 31, 2009 WTM Restricted Stock | Mar. 31, 2007 WTM Restricted Stock Chairman and CEO | Dec. 31, 2010 WTM Restricted Stock Chairman and CEO installments | Mar. 31, 2010 Restricted shares that will vest in December, 2012 | Dec. 31, 2009 Restricted shares cliff that will vest in November, 2010 | Dec. 31, 2009 Restricted shares cliff that will vest in December, 2010 | Dec. 31, 2009 Restricted shares that vest in three equal annual installments beginning in December 2011
Activity in plan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning of period (in shares) |  |  |  |  | 46,250 | 46,250 | 91,900 | 53,200 |  |  |  |  |  |
Issued (in shares) | 27,250 | 19,750 | 47,820 | 250 | 27,000 | 27,250 | 19,750 | 47,100 | 15,000 |  | 19,750 | 2,500 | 40,100 | 4,500
Vested (in shares) |  |  |  |  |  | (1,500) | (65,150) | (8,400) |  |  |  |  |  |
Cancellations and change in assumed forfeitures (in shares) |  |  |  |  |  |  | (250) |  |  |  |  |  |  |
Ending of period (in shares) |  |  |  |  |  | 72,000 | 46,250 | 91,900 |  |  |  |  |  |
Unamortized grant date fair value |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unamortized grant date fair value, beginning balance |  |  |  |  | $ 14.1 | $ 14.1 | $ 23.7 | $ 24.2 |  |  |  |  |  |
Issued |  |  |  |  |  | 9.9 | 6.7 | 9.6 |  |  |  |  |  |
Forfeited |  |  |  |  |  |  | (0.1) |  |  |  |  |  |  |
Modified |  |  |  |  |  |  | (3.3) |  |  |  |  |  |  |
Expense recognized |  |  |  |  |  | (10.7) | (12.9) | (10.1) |  |  |  |  |  |
Unamortized grant date fair value, ending balance |  |  |  |  |  | $ 13.3 | $ 14.1 | $ 23.7 |  |  |  |  |  |
Number of installments in which the shares vest (in installments) |  |  |  |  |  |  |  |  |  | 3 |  |  |  |

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- Definition Equity-based compensation cost during the period with respect to the award, which will be recognized in income (as well as the total recognized tax benefit) or capitalized as part of the cost of an asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 50 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6406099&loc=d3e25284-112666 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph 64, 65 -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 A240 -Subparagraph g(1) -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 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(2)(a) -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 Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(2)(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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(2)(d) -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 (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition An excess of the fair value of the modified award over the fair value of the award immediately before the modification. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph g(2) -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 (h)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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