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Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums written9false 5us-gaap_DeferredRevenuePeriodIncreaseDecreaseus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-58900000-58900000USD$falsefalsefalse2truefalsefalse-64400000-64400000USD$falsefalsefalse3truefalsefalse-125200000-125200000USD$falsefalsefalse4truefalsefalse-123900000-123900000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe net addition or reduction in the carrying amount of deferred revenue during the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 13.A.4(a).(Q1)) -URI http://asc.fasb.org/extlink&oid=6600647&loc=d3e214044-122780 false2Change in net unearned premiums10false 5us-gaap_PremiumsEarnedNetPropertyAndCasualtyus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse138900000138900000USD$falsefalsefalse2truefalsefalse146400000146400000USD$falsefalsefalse3truefalsefalse298600000298600000USD$falsefalsefalse4truefalsefalse306900000306900000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums recognized as revenue in the period earned on all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums earned11false 5us-gaap_IncurredClaimsPropertyCasualtyAndLiabilityus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-46800000-46800000USD$falsefalsefalse2truefalsefalse-57200000-57200000USD$falsefalsefalse3truefalsefalse-97400000-97400000USD$falsefalsefalse4truefalsefalse-101200000-101200000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryProvision for benefits, claims and claims settlement expenses incurred during the period for property and casualty insurance net of the effects of contracts assumed and ceded.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 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5 -Article 7 false2Loss and LAE12false 5us-gaap_DeferredPolicyAcquisitionCostAmortizationExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-22600000-22600000USD$falsefalsefalse2truefalsefalse-23600000-23600000USD$falsefalsefalse3truefalsefalse-44700000-44700000USD$falsefalsefalse4truefalsefalse-48400000-48400000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred policy acquisition costs charged to expense in the period, generally in proportion to related revenue earned, estimated gross profits, or over the customer relationship or some other period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 95-1 -Paragraph 19, 20, 21, 22, 23 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.7(a)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 7 -Article 7 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 60 -Paragraph 60 -Subparagraph c -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6967983&loc=d3e11264-158415 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 35 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=7473040&loc=d3e10157-158409 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6480726&loc=d3e6691-158385 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 97 -Paragraph 22, 23, 24, 25, 26 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Acquisition costs13false 5us-gaap_GeneralAndAdministrativeExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-26400000-26400000USD$falsefalsefalse2truefalsefalse-31000000-31000000USD$falsefalsefalse3truefalsefalse-53300000-53300000USD$falsefalsefalse4truefalsefalse-56700000-56700000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 false2General and administrative expenses14false 5mrh_InsuranceUnderwritingIncomeLossmrh_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse4310000043100000USD$falsefalsefalse2truefalsefalse3460000034600000USD$falsefalsefalse3truefalsefalse103200000103200000USD$falsefalsefalse4truefalsefalse100600000100600000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents earned premium, less claims- and premium-related costs and administrative expenses.No definition available.true2Underwriting income15false 5us-gaap_NetInvestmentIncomeus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1670000016700000USD$falsefalsefalse2truefalsefalse1720000017200000USD$falsefalsefalse3truefalsefalse3310000033100000USD$falsefalsefalse4truefalsefalse3480000034800000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe income earned from investments in securities and property, equipment and other capital assets. 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This amount includes premium assumed from other insurers.No definition available.false2Gross premiums written26false 5us-gaap_CededPremiumsWrittenPropertyAndCasualtyus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-32300000-32300000USD$falsefalsefalse2truefalsefalse-40500000-40500000USD$falsefalsefalse3truefalsefalse-58200000-58200000USD$falsefalsefalse4truefalsefalse-67100000-67100000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums for property and casualty coverage ceded to another insurer under reinsurance arrangements.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Ceded reinsurance premiums27false 5us-gaap_PremiumsWrittenNetPropertyAndCasualtyus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse128300000128300000USD$falsefalsefalse2truefalsefalse146400000146400000USD$falsefalsefalse3truefalsefalse278300000278300000USD$falsefalsefalse4truefalsefalse300500000300500000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums written for all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums written28false 5us-gaap_DeferredRevenuePeriodIncreaseDecreaseus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-44200000-44200000USD$falsefalsefalse2truefalsefalse-61500000-61500000USD$falsefalsefalse3truefalsefalse-93000000-93000000USD$falsefalsefalse4truefalsefalse-117300000-117300000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe net addition or reduction in the carrying amount of deferred revenue during the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 13.A.4(a).(Q1)) -URI http://asc.fasb.org/extlink&oid=6600647&loc=d3e214044-122780 false2Change in net unearned premiums29false 5us-gaap_PremiumsEarnedNetPropertyAndCasualtyus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse8410000084100000USD$falsefalsefalse2truefalsefalse8490000084900000USD$falsefalsefalse3truefalsefalse185300000185300000USD$falsefalsefalse4truefalsefalse183200000183200000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums recognized as revenue in the period earned on all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums earned30false 5us-gaap_IncurredClaimsPropertyCasualtyAndLiabilityus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-18900000-18900000USD$falsefalsefalse2truefalsefalse-19500000-19500000USD$falsefalsefalse3truefalsefalse-26200000-26200000USD$falsefalsefalse4truefalsefalse-35700000-35700000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryProvision for benefits, claims and claims settlement expenses incurred during the period for property and casualty insurance net of the effects of contracts assumed and ceded.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 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5 -Article 7 false2Loss and LAE31false 5us-gaap_DeferredPolicyAcquisitionCostAmortizationExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-10000000-10000000USD$falsefalsefalse2truefalsefalse-8900000-8900000USD$falsefalsefalse3truefalsefalse-18800000-18800000USD$falsefalsefalse4truefalsefalse-21100000-21100000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred policy acquisition costs charged to expense in the period, generally in proportion to related revenue earned, estimated gross profits, or over the customer relationship or some other period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 95-1 -Paragraph 19, 20, 21, 22, 23 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.7(a)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 7 -Article 7 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 60 -Paragraph 60 -Subparagraph c -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6967983&loc=d3e11264-158415 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 35 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=7473040&loc=d3e10157-158409 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6480726&loc=d3e6691-158385 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 97 -Paragraph 22, 23, 24, 25, 26 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Acquisition costs32false 5us-gaap_GeneralAndAdministrativeExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-8600000-8600000USD$falsefalsefalse2truefalsefalse-11000000-11000000USD$falsefalsefalse3truefalsefalse-17800000-17800000USD$falsefalsefalse4truefalsefalse-20900000-20900000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 false2General and administrative expenses33false 5mrh_InsuranceUnderwritingIncomeLossmrh_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse4660000046600000USD$falsefalsefalse2truefalsefalse4550000045500000USD$falsefalsefalse3truefalsefalse122500000122500000USD$falsefalsefalse4truefalsefalse105500000105500000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents earned premium, less claims- and premium-related costs and administrative expenses.No definition available.true2Underwriting income34false 5us-gaap_NetInvestmentIncomeus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1520000015200000USD$falsefalsefalse2truefalsefalse1640000016400000USD$falsefalsefalse3truefalsefalse3000000030000000USD$falsefalsefalse4truefalsefalse3320000033200000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe income earned from investments in securities and property, equipment and other capital assets. 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Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 18 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.18) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 7 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Concepts (CON) -Number 6 -Paragraph 25 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Total Assets43true 4mrh_IncomeAbstractmrh_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Income44false 5mrh_GrossPremiumsWrittenmrh_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsepositiveLabel1truefalsefalse5890000058900000USD$falsefalsefalse2truefalsefalse6340000063400000USD$falsefalsefalse3truefalsefalse128700000128700000USD$falsefalsefalse4truefalsefalse138100000138100000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryTotal consideration paid and payable by direct and assumed policyholders for insurance and reinsurance contracts sold by the Entity during the period. This amount includes premium assumed from other insurers.No definition available.false2Gross premiums written45false 5us-gaap_CededPremiumsWrittenPropertyAndCasualtyus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-9300000-9300000USD$falsefalsefalse2truefalsefalse-1600000-1600000USD$falsefalsefalse3truefalsefalse-18000000-18000000USD$falsefalsefalse4truefalsefalse-11700000-11700000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums for property and casualty coverage ceded to another insurer under reinsurance arrangements.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Ceded reinsurance premiums46false 5us-gaap_PremiumsWrittenNetPropertyAndCasualtyus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse4960000049600000USD$falsefalsefalse2truefalsefalse6180000061800000USD$falsefalsefalse3truefalsefalse110700000110700000USD$falsefalsefalse4truefalsefalse126400000126400000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums written for all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums written47false 5us-gaap_DeferredRevenuePeriodIncreaseDecreaseus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-600000-600000USD$falsefalsefalse2truefalsefalse-9100000-9100000USD$falsefalsefalse3truefalsefalse-7300000-7300000USD$falsefalsefalse4truefalsefalse-22900000-22900000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe net addition or reduction in the carrying amount of deferred revenue during the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 13.A.4(a).(Q1)) -URI http://asc.fasb.org/extlink&oid=6600647&loc=d3e214044-122780 false2Change in net unearned premiums48false 5us-gaap_PremiumsEarnedNetPropertyAndCasualtyus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse4900000049000000USD$falsefalsefalse2truefalsefalse5270000052700000USD$falsefalsefalse3truefalsefalse103400000103400000USD$falsefalsefalse4truefalsefalse103500000103500000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums recognized as revenue in the period earned on all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums earned49false 5us-gaap_IncurredClaimsPropertyCasualtyAndLiabilityus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-25400000-25400000USD$falsefalsefalse2truefalsefalse-32200000-32200000USD$falsefalsefalse3truefalsefalse-68500000-68500000USD$falsefalsefalse4truefalsefalse-51800000-51800000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryProvision for benefits, claims and claims settlement expenses incurred during the period for property and casualty insurance net of the effects of contracts assumed and ceded.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 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5 -Article 7 false2Loss and LAE50false 5us-gaap_DeferredPolicyAcquisitionCostAmortizationExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-11900000-11900000USD$falsefalsefalse2truefalsefalse-11800000-11800000USD$falsefalsefalse3truefalsefalse-24800000-24800000USD$falsefalsefalse4truefalsefalse-20400000-20400000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred policy acquisition costs charged to expense in the period, generally in proportion to related revenue earned, estimated gross profits, or over the customer relationship or some other period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 95-1 -Paragraph 19, 20, 21, 22, 23 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums written66false 5us-gaap_DeferredRevenuePeriodIncreaseDecreaseus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-14100000-14100000USD$falsefalsefalse2truefalsefalse-2000000-2000000USD$falsefalsefalse3truefalsefalse-24900000-24900000USD$falsefalsefalse4truefalsefalse-2000000-2000000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe net addition or reduction in the carrying amount of deferred revenue during the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 13.A.4(a).(Q1)) -URI http://asc.fasb.org/extlink&oid=6600647&loc=d3e214044-122780 false2Change in net unearned premiums67false 5us-gaap_PremiumsEarnedNetPropertyAndCasualtyus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse55000005500000USD$falsefalsefalse2truefalsefalse400000400000USD$falsefalsefalse3truefalsefalse93000009300000USD$falsefalsefalse4truefalsefalse400000400000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums recognized as revenue in the period earned on all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Acquisition costs70false 5us-gaap_GeneralAndAdministrativeExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-900000-900000USD$falsefalsefalse2truefalsefalse-800000-800000USD$falsefalsefalse3truefalsefalse-1600000-1600000USD$falsefalsefalse4truefalsefalse-800000-800000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 false2General and administrative expenses71false 5mrh_InsuranceUnderwritingIncomeLossmrh_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse20000002000000USD$falsefalsefalse2truefalsefalse-400000-400000USD$falsefalsefalse3truefalsefalse48000004800000USD$falsefalsefalse4truefalsefalse-400000-400000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents earned premium, less claims- and premium-related costs and administrative expenses.No definition available.true2Underwriting income72false 5us-gaap_OtherIncomeus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse200000200000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse700000700000USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryReflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement.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 210.7-04.4) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 4 -Article 7 false2Other revenue73false 5us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterestus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse22000002200000USD$falsefalsefalse2truefalsefalse-400000-400000USD$falsefalsefalse3truefalsefalse55000005500000USD$falsefalsefalse4truefalsefalse-400000-400000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThis element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 10 -Article 5 true2Income (loss) before income taxes74false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse21false USDtruefalse$D2013Q2_MusicMemberhttp://www.sec.gov/CIK0001165880duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseMUSIC Run-Offus-gaap_StatementBusinessSegmentsAxisxbrldihttp://xbrl.org/2006/xbrldimrh_MusicMemberus-gaap_StatementBusinessSegmentsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0MUSIC Run-Off75true 4us-gaap_AssetsAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Assets76false 5us-gaap_Assetsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse3990000039900000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse3990000039900000USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse4890000048900000USD$falsefalsefalsexbrli:monetaryItemTypemonetarySum of the carrying amounts as of the balance sheet date of all assets that are recognized. 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Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums written80false 5us-gaap_DeferredRevenuePeriodIncreaseDecreaseus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2truefalsefalse82000008200000USD$falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse1830000018300000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe net addition or reduction in the carrying amount of deferred revenue during the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 13.A.4(a).(Q1)) -URI http://asc.fasb.org/extlink&oid=6600647&loc=d3e214044-122780 false2Change in net unearned premiums81false 5us-gaap_PremiumsEarnedNetPropertyAndCasualtyus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse300000300000USD$falsefalsefalse2truefalsefalse84000008400000USD$falsefalsefalse3truefalsefalse600000600000USD$falsefalsefalse4truefalsefalse1980000019800000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums recognized as revenue in the period earned on all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 true2Net insurance and reinsurance premiums earned82false 5us-gaap_IncurredClaimsPropertyCasualtyAndLiabilityus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-500000-500000USD$falsefalsefalse2truefalsefalse-5500000-5500000USD$falsefalsefalse3truefalsefalse-700000-700000USD$falsefalsefalse4truefalsefalse-13700000-13700000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryProvision for benefits, claims and claims settlement expenses incurred during the period for property and casualty insurance net of the effects of contracts assumed and ceded.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5 -Article 7 false2Loss and LAE83false 5us-gaap_DeferredPolicyAcquisitionCostAmortizationExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-100000-100000USD$falsefalsefalse2truefalsefalse-2900000-2900000USD$falsefalsefalse3truefalsefalse-200000-200000USD$falsefalsefalse4truefalsefalse-6900000-6900000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred policy acquisition costs charged to expense in the period, generally in proportion to related revenue earned, estimated gross profits, or over the customer relationship or some other period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 95-1 -Paragraph 19, 20, 21, 22, 23 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.7(a)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 7 -Article 7 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 60 -Paragraph 60 -Subparagraph c -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6967983&loc=d3e11264-158415 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 35 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=7473040&loc=d3e10157-158409 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6480726&loc=d3e6691-158385 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 97 -Paragraph 22, 23, 24, 25, 26 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Acquisition costs84false 5mrh_InsuranceUnderwritingIncomeLossmrh_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-300000-300000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse-300000-300000USD$falsefalsefalse4truefalsefalse-800000-800000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents earned premium, less claims- and premium-related costs and administrative expenses.No definition available.true2Underwriting income85false 5us-gaap_NetInvestmentIncomeus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse200000200000USD$falsefalsefalse2truefalsefalse300000300000USD$falsefalsefalse3truefalsefalse400000400000USD$falsefalsefalse4truefalsefalse600000600000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe income earned from investments in securities and property, equipment and other capital assets. 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It does not include realized gains and losses on investments.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.2) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 2 -Article 7 false2Net investment income86false 5mrh_ForeignCurrencyTransactionGainLossAndInvestmentmrh_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-700000-700000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse-800000-800000USD$falsefalsefalse4truefalsefalse300000300000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents the aggregate foreign currency transaction gain (loss) and investment income included in determining net income for the reporting period.No definition available.false2Net investment and foreign exchange gains (losses)87false 5us-gaap_OtherIncomeus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse200000200000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryReflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement.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 210.7-04.4) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 4 -Article 7 false2Other revenue88false 5us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterestus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-800000-800000USD$falsefalsefalse2truefalsefalse300000300000USD$falsefalsefalse3truefalsefalse-700000-700000USD$falsefalsefalse4truefalsefalse300000300000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThis element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 10 -Article 5 true2Income (loss) before income taxes89false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse26false USDtruefalse$D2013Q2_AllOtherSegmentsMemberhttp://www.sec.gov/CIK0001165880duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseCorporate and Other, including intercompany eliminationsus-gaap_StatementBusinessSegmentsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_AllOtherSegmentsMemberus-gaap_StatementBusinessSegmentsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Corporate and Other, including intercompany eliminations90true 4us-gaap_AssetsAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Assets91false 5us-gaap_Assetsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse69000006900000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse69000006900000USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse78000007800000USD$falsefalsefalsexbrli:monetaryItemTypemonetarySum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 18 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.18) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 7 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Concepts (CON) -Number 6 -Paragraph 25 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. 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This amount includes premium assumed from other insurers.No definition available.false2Gross premiums written94false 5us-gaap_CededPremiumsWrittenPropertyAndCasualtyus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-300000-300000USD$falsefalsefalse2truefalsefalse-600000-600000USD$falsefalsefalse3truefalsefalse-900000-900000USD$falsefalsefalse4truefalsefalse-3600000-3600000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryPremiums for property and casualty coverage ceded to another insurer under reinsurance arrangements.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Ceded reinsurance premiums95false 5us-gaap_GeneralAndAdministrativeExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-9000000-9000000USD$falsefalsefalse2truefalsefalse-8000000-8000000USD$falsefalsefalse3truefalsefalse-17700000-17700000USD$falsefalsefalse4truefalsefalse-15200000-15200000USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 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