XML 151 R131.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net income (loss) attributable to White Mountains’ common shareholders |  |  |  |  |  |  |  |  | $ (2.3) | $ 200.7 | $ 53.2
Basic and diluted earnings per share numerators (in millions): |  |  |  |  |  |  |  |  |  |  |
Allocation of income for unvested restricted common shares(1) |  |  |  |  |  |  |  |  | 0.0 | (2.3) | (0.7)
Dividends declared on participating restricted common shares(1) |  |  |  |  |  |  |  |  | 0.0 | (0.1) | (0.1)
Total allocation to restricted common shares |  |  |  |  |  |  |  |  | 0.0 | (2.4) | (0.8)
Net income attributable to White Mountains’s common shareholders, net of restricted common share amounts |  |  |  |  |  |  |  |  | (2.3) | 198.3 | 52.4
Undistributed net earnings (in millions): |  |  |  |  |  |  |  |  |  |  |
Net income attributable to White Mountains’s common shareholders, net of restricted common share amounts |  |  |  |  |  |  |  |  | (2.3) | 198.3 | 52.4
Dividends declared net of restricted common share amounts(1) |  |  |  |  |  |  |  |  | (5.4) | (5.9) | (6.1)
Total undistributed net earnings, net of restricted common share amounts |  |  |  |  |  |  |  |  | $ (7.7) | $ 192.4 | $ 46.3
Basic earnings per share denominators (in thousands): |  |  |  |  |  |  |  |  |  |  |
Total average common shares outstanding during the period |  |  |  |  |  |  |  |  | 5,014,900 | 5,879,200 | 6,104,900
Average unvested restricted common shares |  |  |  |  |  |  |  |  | (64,800) | (68,000) | (78,900)
Basic earnings per share denominator |  |  |  |  |  |  |  |  | 4,950,100 | 5,811,200 | 6,026,000
Diluted earnings per share denominator (in thousands): |  |  |  |  |  |  |  |  |  |  |
Average outstanding dilutive shares outstanding |  |  |  |  |  |  |  |  | 5,018,100 | 5,879,200 | 6,104,900
Average unvested restricted common shares |  |  |  |  |  |  |  |  | (64,800) | (68,000) | (78,900)
Diluted earnings (loss) per share denominator |  |  |  |  |  |  |  |  | 4,953,300 | 5,811,200 | 6,026,000
Basic earnings per share (in dollars): |  |  |  |  |  |  |  |  |  |  |
Net income attributable to White Mountains’s common shareholders | $ (5.81) | $ 6.12 | $ (3.44) | $ 2.51 | $ 43.82 | $ (11.10) | $ 0.80 | $ 1.76 | $ (0.47) | $ 34.12 | $ 8.70
Dividends declared and paid |  |  |  |  |  |  |  |  | (1.00) | (1.00) | (1.00)
Undistributed (loss) earnings |  |  |  |  |  |  |  |  | (1.47) | 33.12 | 7.70
Diluted earnings per share (in dollars) |  |  |  |  |  |  |  |  |  |  |
Net income attributable to White Mountains’s common shareholders | $ (5.81) | $ 6.11 | $ (3.43) | $ 2.51 | $ 43.79 | $ (11.10) | $ 0.80 | $ 1.76 | (0.47) | 34.12 | 8.70
Dividends declared and paid |  |  |  |  |  |  |  |  | (1.00) | (1.00) | (1.00)
Undistributed (loss) earnings |  |  |  |  |  |  |  |  | $ (1.47) | $ 33.12 | $ 7.70

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate dividends declared during the period for each share of common stock outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
Name: | us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared and applicable to holders of share-based compensation, for example, but not limited to, non-vested shares, stock options, or restricted stock units. + References No definition available. + Details
Name: | us-gaap_DividendsShareBasedCompensation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_EarningsPerShareBasicAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_EarningsPerShareBasicAndDilutedAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The earnings attributable to each security on the basis that all of the earnings for the period had been distributed (to the extent that each security may share in earnings). This is the earnings amount which reflects the participation rights in undistributed earnings of each security. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 66 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e2814-109256 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e2740-109256 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 65 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e2793-109256 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60A -URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5780132-109256 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60B -URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5780133-109256 + Details
Name: | us-gaap_EarningsPerShareBasicUndistributed
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_EarningsPerShareDilutedAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The earnings attributable to each security on the basis that all of the earnings for the period had been distributed (to the extent that each security may share in earnings). This is the earnings amount which reflects the participation rights in undistributed earnings of each security, after giving effect to all dilutive potential common shares outstanding during the period. + References No definition available. + Details
Name: | us-gaap_EarningsPerShareDilutedUndistributed
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount after tax of income (loss) from continuing operations attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -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 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.13) -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 810 -SubTopic 10 -Section 45 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=68079674&loc=SL4613673-111683 + Details
Name: | us-gaap_IncomeLossFromContinuingOperations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period. + References Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(19)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 3: 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(20)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-03(13)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20187-122688 Reference 5: 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 Reference 6: 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 7: 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(11)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 + Details
Name: | us-gaap_IncomeLossFromContinuingOperationsPerBasicShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of net income (loss) derived from continuing operations during 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 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: 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 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-03(13)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20187-122688 Reference 4: 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 5: 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(11)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 6: 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 7: 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 + Details
Name: | us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition The earnings that is allocated to common stock and participating securities to the extent that each security may share in earnings as if all of the earnings for the period had been distributed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 65 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e2793-109256 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60A -URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5780132-109256 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 66 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e2814-109256 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e2740-109256 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60B -URI http://asc.fasb.org/extlink&oid=64863997&loc=SL5780133-109256 + Details
Name: | us-gaap_UndistributedEarnings
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_UndistributedEarningsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
Name: | us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in 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 16 -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e1505-109256 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
Name: | us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- 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
Name: | us-gaap_WeightedAverageNumberOfSharesIssuedBasic
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Weighted-Average Number of Common Shares Outstanding -URI http://asc.fasb.org/extlink&oid=6528421 + Details
Name: | us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares of restricted stock determined by relating the portion of time within a reporting period that restricted shares have been outstanding to the total time in that period. Restricted shares are subject to sales, contractual, regulatory or other restrictions that prevent or inhibit the holder from freely disposing of them before the restriction ends. + References Reference 1: 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
Name: | us-gaap_WeightedAverageNumberOfSharesRestrictedStock
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the total amount allocated to restricted shares including dividend on restricted stock. + References No definition available. + Details
Name: | wtm_AggregateAllocationToRestrictedSharesIncludingDividend
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Equity impact of common stock cash dividends declared by the entity during the period, net of restricted share amounts. + References No definition available. + Details
Name: | wtm_DividendsCommonStockCashNetOfRestrictedCommonShareAmounts
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents the portion of income (loss) allocated to participating unvested restricted common shares. + References No definition available. + Details
Name: | wtm_IncomeLossAllocatedToParticipatingUnvestedRestrictedCommonShares
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents Net income from continuing operations attributable to White Mountains common shareholders, net of allocation to restricted shares and dividends paid on restricted shares. + References No definition available. + Details
Name: | wtm_IncomeLossFromContinuingOperatingsExcludingPortionAttributableToNoncontrollingInterestNet
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration