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Employee Share-Based Incentive Compensation Plans (Tables) | 12 Months Ended
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Dec. 31, 2014
White Mountains |
Share-based compensation arrangement by share-based payment award |
Summary of performance share activity | The following summarizes performance share activity for the years ended December 31, 2014, 2013 and 2012 for performance shares granted under the WTM Incentive Plan and the WTM Phantom Share Plan:
|  | Year Ended December 31,
|  | 2014 |  | 2013 |  | 2012
Millions, except share amounts |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense
Beginning of period |  | 119,220 |  |  | $ | 60.2 |  |  | 119,357 |  |  | $ | 29.4 |  |  | 150,064 |  |  | $ | 66.1 |
Shares paid or expired(1) |  | (37,130 | ) |  | (26.7 | ) |  | (47,310 | ) |  | (11.0 | ) |  | (68,357 | ) |  | (58.3 | )
New grants |  | 45,660 |  |  | — |  |  | 47,170 |  |  | — |  |  | 38,432 |  |  | — |
Assumed forfeitures and cancellations(2)(3) |  | (4,201 | ) |  | (.7 | ) |  | 3 |  |  | (.6 | ) |  | (782 | ) |  | .6 |
Expense recognized |  | — |  |  | 15.3 |  |  | — |  |  | 42.4 |  |  | — |  |  | 21.0 |
Ending December 31, |  | 123,549 |  |  | $ | 48.1 |  |  | 119,220 |  |  | $ | 60.2 |  |  | 119,357 |  |  | $ | 29.4 |
(1) | WTM performance shares payments in 2014 for the 2011-2013 performance cycle ranged from 88% to 131.5% of target. WTM performance shares payments in 2013 for the 2010-2012 performance cycle ranged from 33% to 98% of target. WTM performance share payments in 2012 for the 2009-2011 performance cycle ranged from 147% to 155% of target. As of December 31, 2012, White Mountains paid $9.9 as a partial payment for the 2010-2012 performance cycle.
(2) | On November 19, 2014, the Compensation Committee canceled 3,040 WTM performance shares for the 2014-2016 performance cycle and issued the same number of WTM restricted shares.
(3) | Amounts include changes in assumed forfeitures, as required under GAAP.
Summary of performance shares outstanding and accrued expense for performance shares awarded under an Incentive Plan | The following table summarizes performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of December 31, 2014 for each performance cycle:
Millions, except share amounts |  | Target WTM Performance Shares Outstanding |  | Accrued Expense
Performance cycle: |  |  |  |  |  |
2014 – 2016 |  | 41,937 |  |  | $ | 4.1 |
2013 – 2015 |  | 46,803 |  |  | 18.9 |
2012 – 2014 |  | 37,977 |  |  | 26.4 |
Sub-total |  | 126,717 |  |  | 49.4 |
Assumed forfeitures |  | (3,168 | ) |  | (1.3 | )
Total at December 31, 2014 |  | 123,549 |  |  | $ | 48.1 |
Schedule of Nonvested Restricted Stock Activity [Table Text Block] | The following outlines the unrecognized compensation cost associated with the outstanding restricted share awards under the WTM Incentive Plan for the years ended December 31, 2014, 2013 and 2012:
|  | Year Ended December 31,
|  | 2014 |  | 2013 |  | 2012
Millions, except share amounts |  | Restricted Shares | Unamortized Issue Date Fair Value |  | Restricted Shares | Unamortized Issue Date Fair Value |  | Restricted Shares | Unamortized Issue Date Fair Value
Non-vested, |  |  |  |  |  |  |  |  |
Beginning of period |  | 94,130 |  | $ | 17.0 |  |  | 69,910 |  | $ | 16.8 |  |  | 72,000 |  | $ | 13.3 |
Issued (1) |  | 23,440 |  | 13.1 |  |  | 25,720 |  | 14.4 |  |  | 32,160 |  | 15.7 |
Vested (2) |  | (33,205 | ) | — |  |  | (1,500 | ) | — |  |  | (32,945 | ) | — |
Forfeited |  | (1,051 | ) | (.5 | ) |  | — |  | — |  |  | (1,305 | ) | (.2 | )
Expense recognized |  | — |  | (15.3 | ) |  | — |  | (14.2 | ) |  | — |  | (12.0 | )
Non-vested at December 31, |  | 83,314 |  | $ | 14.3 |  |  | 94,130 |  | $ | 17.0 |  |  | 69,910 |  | $ | 16.8 |
(1) | During 2012, the Compensation Committee accelerated the vesting date for an installment of 5,000 restricted shares from January 20, 2013 to December 31, 2012.
(2) | On November 19, 2014, the Compensation Committee canceled 3,040 WTM performance shares for the 2014-2016 performance cycle and issued the same number of WTM restricted shares.
OneBeacon |
Share-based compensation arrangement by share-based payment award |
Summary of performance share activity | The following summarizes activity for the years ended December 31, 2014, 2013 and 2012 for OneBeacon performance shares granted under the OneBeacon Incentive Plan:
|  | Year Ended December 31,
|  | 2014 |  | 2013 |  | 2012
Millions, except share amounts |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense
Beginning of period |  | 493,421 |  |  | $ | 4.0 |  |  | 563,190 |  |  | $ | 1.2 |  |  | 642,667 |  |  | $ | 9.7 |
Payments and deferrals(1) |  | (142,138 | ) |  | (1.0 | ) |  | (238,658 | ) |  | — |  |  | (258,901 | ) |  | (7.7 | )
New awards |  | 165,800 |  |  | — |  |  | 179,000 |  |  | — |  |  | 181,290 |  |  | — |
Forfeitures and cancellations(2) |  | 387 |  |  | — |  |  | (10,111 | ) |  | (.1 | ) |  | (1,866 | ) |  | — |
Expense recognized |  | — |  |  | .4 |  |  | — |  |  | 2.9 |  |  | — |  |  | (.8 | )
End of period |  | 517,470 |  |  | $ | 3.4 |  |  | 493,421 |  |  | $ | 4.0 |  |  | 563,190 |  |  | $ | 1.2 |
(1) | OneBeacon performance share payments in 2014 for the 2011-2013 performance cycle were at 37.1% of target. No payments were made in 2013 for the 2010-2012 OneBeacon performance cycle as the performance factor was zero. OneBeacon performance share payments in 2012 for the 2009-2011 performance cycle were at 138.6% of target.
(2) | Amounts include changes in assumed forfeitures, as required under GAAP.
Summary of performance shares outstanding and accrued expense for performance shares awarded under an Incentive Plan | The following summarizes OneBeacon performance shares outstanding awarded under the OneBeacon Incentive Plan as of December 31, 2014 for each performance cycle:
Millions, except share amounts |  | Target OneBeacon Performance Shares Outstanding |  | Accrued Expense
Performance cycle: |  |  |  |  |  |
2014 – 2016 |  | 165,800 |  |  | $ | .5 |
2013 – 2015 |  | 179,000 |  |  | 1.4 |
2012 – 2014 |  | 181,290 |  |  | 1.5 |
Sub-total |  | 526,090 |  |  | 3.4 |
Assumed forfeitures |  | (8,620 | ) |  | — |
Total at December 31, 2014 |  | 517,470 |  |  | $ | 3.4 |
Schedule of Nonvested Restricted Stock Activity [Table Text Block] | The following table summarizes the unrecognized compensation cost associated with the outstanding OneBeacon restricted stock awards for the years ended December 31, 2014, 2013 and 2012.
|  | Year Ended December 31,
|  | 2014 |  | 2013 |  | 2012
Millions, except share amounts |  | Restricted Shares |  | Unamortized Issue Date Fair Value |  | Restricted Shares |  | Unamortized Issue Date Fair Value |  | Restricted Shares |  | Unamortized Issue Date Fair Value
Non-vested, |  |  |  |  |  |  |  |  |  |  |  |
Beginning of period |  | 915,000 |  |  | $ | 6.5 |  |  | 927,000 |  |  | $ | 9.6 |  |  | 630,000 |  |  | $ | 7.7 |
Issued |  | — |  |  | — |  |  | — |  |  | — |  |  | 300,000 |  |  | 4.5 |
Vested |  | (300,000 | ) |  | — |  |  | (9,000 | ) |  | — |  |  | (667 | ) |  | — |
Forfeited |  | (2,500 | ) |  | — |  |  | (3,000 | ) |  | — |  |  | (2,333 | ) |  | — |
Expense recognized |  | — |  |  | (3.0 | ) |  | — |  |  | (3.1 | ) |  | — |  |  | (2.6 | )
End of period |  | 612,500 |  |  | $ | 3.5 |  |  | 915,000 |  |  | $ | 6.5 |  |  | 927,000 |  |  | $ | 9.6 |

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