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Discontinued Operations - EPS (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Basic and diluted earnings per share numerators (in millions): |  |  |  |
Allocation of income for participating unvested restricted common shares | $ (0.2) | $ 0.6 | $ (0.1) | $ 0.9
Net income attributable to White Mountains’s common shareholders | $ 15.5 | $ 341.1 | $ 49.8 | $ 354.1
Basic earnings per share denominators |  |  |  |
Total average common shares outstanding during the period | 4,572,100 | 5,096,100 | 4,568,400 | 5,317,800
Average unvested restricted common shares | (57,200) | (66,500) | (54,900) | (60,200)
Basic earnings per share denominator | 4,514,900 | 5,029,600 | 4,513,500 | 5,257,600
Diluted earnings per share denominator |  |  |  |
Total average common shares outstanding during the period | 4,572,100 | 5,107,000 | 4,568,400 | 5,324,000
Average unvested restricted common shares | (57,200) | (66,500) | (54,900) | (60,200)
Diluted earnings per share denominator | 4,514,900 | 5,040,500 | 4,513,500 | 5,263,800
Basic earnings per share (in dollars) | $ 3.39 | $ 66.93 | $ 10.89 | $ 66.57
Diluted earnings per share (in dollars) | $ 3.39 | $ 66.79 | $ 10.89 | $ 66.50
Incremental common shares attributable to dilutive effect of share-based payment arrangements |  | 10,863 |  | 6,194
Discontinued Operations |  |  |  |
Basic and diluted earnings per share numerators (in millions): |  |  |  |
Net income attributable to White Mountains’s common shareholders | $ 2.8 | $ 383.6 | $ 34.1 | $ 431.0
Allocation of income for participating unvested restricted common shares | 0.0 | (5.0) | (0.4) | (4.9)
Net income attributable to White Mountains’s common shareholders | $ 2.8 | $ 378.6 | $ 33.7 | $ 426.1
Basic earnings per share denominators |  |  |  |
Total average common shares outstanding during the period | 4,572,100 | 5,096,100 | 4,568,400 | 5,317,800
Average unvested restricted common shares | (57,200) | (66,500) | (54,900) | (60,200)
Basic earnings per share denominator | 4,514,900 | 5,029,600 | 4,513,500 | 5,257,600
Diluted earnings per share denominator |  |  |  |
Total average common shares outstanding during the period | 4,572,100 | 5,107,000 | 4,568,400 | 5,324,000
Average unvested restricted common shares | (57,200) | (66,500) | (54,900) | (60,200)
Diluted earnings per share denominator | 4,514,900 | 5,040,500 | 4,513,500 | 5,263,800
Basic earnings per share (in dollars) | $ 0.61 | $ 75.27 | $ 7.47 | $ 81.04
Diluted earnings per share (in dollars) | $ 0.61 | $ 75.11 | $ 7.47 | $ 80.96
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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- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(19)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e1252-109256 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(21)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(23)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e1377-109256 + Details
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- Definition This element represents the weighted average total number of shares issued throughout the period including the first (beginning balance outstanding) and last (ending balance outstanding) day of the period before considering any reductions (for instance, shares held in treasury) to arrive at the weighted average number of shares outstanding. Weighted average relates to the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Such concept is used in determining the weighted average number of shares outstanding for purposes of calculating earnings per share (basic). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e1448-109256 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e2646-109256 + Details
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