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Employee Share-Based Incentive Compensation Plans (WTM Phantom Performance Shares Granted Under WTM Phantom Shares Plan) (Details) (USD $)
In Millions, except Share data, unless otherwise specified |
9 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
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Sep. 30, 2012
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Dec. 31, 2011
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Sep. 30, 2012
Range of Performance Cycle from 2010 to 2012 [Member]
W T M Phantom Share Plans [Member]
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Sep. 30, 2012
Range of Performance Cycle from 2011 to 2013 [Member]
W T M Phantom Share Plans [Member]
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Sep. 30, 2012
Range Of Performance Cycle From 2012 To 2014 [Member]
W T M Phantom Share Plans [Member]
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Sep. 30, 2012
Performance Share [Member]
W T M Phantom Share Plans [Member]
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| Share-based compensation arrangement by share-based payment award | ||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award Equity Instruments Other than Options Nonvested, Number before Forfeitures | 4,990 | 0 | [1] | 0 | [1] | 4,990 | ||||
| Incentive Compensation Payable before Forfeitures | $ 2.7 | $ 0 | [1] | $ 0 | [1] | $ 2.7 | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Assumed Forfeitures in Period | (125) | |||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Assumed Forfeitures in Period Amount | 0.1 | |||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number | 4,865 | |||||||||
| Accrued incentive compensation | $ 144.7 | $ 187.9 | $ 2.6 | |||||||
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