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SELECTED QUARTERLY FINANCIAL DATA (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2010 | Sep. 30, 2010 | Jun. 30, 2010 | Mar. 31, 2010 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
SELECTED QUARTERLY FINANCIAL DATA (Unaudited) |  |  |  |  |  |  |  |  |  |  |
Revenues | $ 593.6 | $ 501.3 | $ 553.6 | $ 529.6 | $ 552.8 | $ 551.0 | $ 670.8 | $ 792.1 | $ 2,178.1 | $ 2,566.7 | $ 3,443.3
Expenses | 535.6 | 500.1 | 517.5 | 563.3 | 457.2 | 475.8 | 664.9 | 815.7 | 2,116.5 | 2,413.6 | 2,646.1
Pre-tax income | 58.0 | 1.2 | 36.1 | (33.7) | 95.6 | 75.2 | 5.9 | (23.6) | 61.6 | 153.1 | 797.2
Tax benefit (expense) | 124.6 | 0.6 | (10.0) | 7.7 | (6.6) | (11.7) | 1.4 |  | 122.7 | (16.9) | (214.2)
Net income from continuing operations | 182.6 | 1.8 | 26.1 | (26.0) | 89.0 | 63.5 | 7.3 | (23.6) | 184.3 | 136.2 | 583.0
Net loss from discontinued operations, net of tax | 674.2 | (30.1) | (1.5) | 2.5 | (7.8) | 3.6 | 0.6 | (3.0) | (13.0) | (6.6) | (27.8)
Noncontrolling interest in consolidated subsidiaries | (20.3) | 11.0 | (20.8) | (11.4) | (16.6) | (24.3) | (10.7) | (1.4) | (41.5) | (53.0) | (109.5)
Equity in (losses) earnings of unconsolidated affiliates | (36.3) | 1.5 | 7.9 | 6.7 | 8.3 | 7.9 | 5.3 | (11.6) | (20.2) | 9.9 | 24.3
Net income attributable to White Mountains' common shareholders | $ 800.2 | $ (15.8) | $ 11.7 | $ (28.2) | $ 72.9 | $ 50.7 | $ 2.5 | $ (39.6) | $ 767.9 | $ 86.5 | $ 470.0
Basic |  |  |  |  |  |  |  |  |  |  |
Continuing operations (in dollars per share) | $ 16.54 | $ 1.81 | $ 1.66 | $ (3.82) | $ 9.77 | $ 5.58 | $ 0.21 | $ (4.14) | $ 15.56 | $ 10.89 | $ 56.25
Discontinued operations (in dollars per share) | $ 88.50 | $ (3.81) | $ (0.18) | $ 0.31 | $ (0.94) | $ 0.43 | $ 0.07 | $ (0.34) | $ 81.88 | $ (0.77) | $ (3.14)
Total consolidated operations (in dollars per share) | $ 105.04 | $ (2.00) | $ 1.48 | $ (3.51) | $ 8.83 | $ 6.01 | $ 0.28 | $ (4.48) | $ 97.44 | $ 10.12 | $ 53.11
Diluted |  |  |  |  |  |  |  |  |  |  |
Continuing operations (in dollars per share) | $ 16.54 | $ 1.81 | $ 1.66 | $ (3.82) | $ 9.77 | $ 5.58 | $ 0.21 | $ (4.14) | $ 15.56 | $ 10.89 | $ 56.24
Discontinued operations (in dollars per share) | $ 88.50 | $ (3.81) | $ (0.18) | $ 0.31 | $ (0.94) | $ 0.43 | $ 0.07 | $ (0.34) | $ 81.88 | $ (0.77) | $ (3.14)
Total consolidated operations (in dollars per share) | $ 105.04 | $ (2.00) | $ 1.48 | $ (3.51) | $ 8.83 | $ 6.01 | $ 0.28 | $ (4.48) | $ 97.44 | $ 10.12 | $ 53.10
Adjusted book value per share (in dollars per share) | $ 542.11 | $ 436.18 | $ 447.69 | $ 446.70 | $ 440.59 | $ 428.79 | $ 405.94 | $ 410.59 |  |  |

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