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Discontinued Operations - EPS (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
Basic and diluted earnings per share numerators (in millions): |  |  |  |
Net income attributable to White Mountains’s common shareholders | $ 562.1 | $ 90.8 | $ 604.7 | $ 440.7
Less: total income from continuing operations, net of tax | 23.0 | 6.4 | 31.5 | (74.7)
Net income (loss) from discontinued operations attributable to White Mountains’s common shareholders | (539.1) | (84.4) | (573.2) | (515.4)
Basic and diluted earnings per share numerators | $ 22.7 | $ 6.3 | $ 31.1 | $ (73.9)
Basic earnings per share denominators |  |  |  |
Total average common shares outstanding during the period | 4,297,200 | 4,867,400 | 4,477,000 | 5,166,600
Average unvested restricted common shares | (53,700) | (68,100) | (54,500) | (62,900)
Basic earnings per share denominator | 4,243,500 | 4,799,300 | 4,422,500 | 5,103,700
Diluted earnings per share denominator |  |  |  |
Total average common shares outstanding during the period | 4,297,200 | 4,879,400 | 4,477,000 | 5,174,800
Average unvested restricted common shares | (53,700) | (68,100) | (54,500) | (62,900)
Diluted earnings per share denominator | 4,243,500 | 4,811,300 | 4,422,500 | 5,111,900
Basic earnings per share (in dollars) | $ 130.81 | $ 18.65 | $ 135.06 | $ 85.28
Diluted earnings per share (in dollars) | $ 130.81 | $ 18.61 | $ 135.06 | $ 85.13
Incremental common shares attributable to dilutive effect of share-based payment arrangements |  | 11,943 |  | 8,208
Discontinued Operations |  |  |  |
Basic and diluted earnings per share numerators (in millions): |  |  |  |
Net income attributable to White Mountains’s common shareholders | $ 562.1 | $ 90.8 | $ 604.7 | $ 440.7
Less: total income from continuing operations, net of tax | (23.0) | (6.4) | (31.5) | 74.7
Net income (loss) from discontinued operations attributable to White Mountains’s common shareholders | 539.1 | 84.4 | 573.2 | 515.4
Allocation of income for participating unvested restricted common shares | (6.7) | (1.2) | (7.0) | (6.3)
Basic and diluted earnings per share numerators | $ 532.4 | $ 83.2 | $ 566.2 | $ 509.1
Basic earnings per share denominators |  |  |  |
Total average common shares outstanding during the period | 4,297,200 | 4,867,400 | 4,477,000 | 5,166,600
Average unvested restricted common shares | (53,700) | (68,100) | (54,500) | (62,900)
Basic earnings per share denominator | 4,243,500 | 4,799,300 | 4,422,500 | 5,103,700
Diluted earnings per share denominator |  |  |  |
Total average common shares outstanding during the period | 4,297,200 | 4,879,400 | 4,477,000 | 5,174,800
Average unvested restricted common shares | (53,700) | (68,100) | (54,500) | (62,900)
Diluted earnings per share denominator | 4,243,500 | 4,811,300 | 4,422,500 | 5,111,900
Basic earnings per share (in dollars) | $ 125.45 | $ 17.34 | $ 128.03 | $ 99.75
Diluted earnings per share (in dollars) | $ 125.45 | $ 17.30 | $ 128.03 | $ 99.60
Employee Stock Option |  |  |  |
Diluted earnings per share denominator |  |  |  |
Incremental common shares attributable to dilutive effect of share-based payment arrangements |  | 120,000 |  | 120,000

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