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value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph a -Clause 1 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959 false2Fair Value, Assets4false 4us-gaap_DerivativeFairValueOfDerivativeLiabilityus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalse9falsefalsefalse00falsefalsefalse10falsefalsefalse00falsefalsefalse11falsefalsefalse00falsefalsefalse12falsefalsefalse00falsefalsefalse13falsefalsefalse00falsefalsefalse14falsefalsefalse00falsefalsefalse15falsefalsefalse00falsefalsefalse16falsefalsefalse00falsefalsefalse17falsefalsefalse00falsefalsefalse18falsefalsefalse00falsefalsefalse19falsefalsefalse00falsefalsefalse20falsefalsefalse00falsefalsefalse21falsefalsefalse00falsefalsefalse22falsefalsefalse00falsefalsefalse23falsefalsefalse00falsefalsefalse24falsefalsefalse00falsefalsefalse25falsefalsefalse00falsefalsefalse26truefalsefalse2000000.2falsefalsefalse27truefalsefalse00falsefalsefalse28falsefalsefalse00falsefalsefalse29falsefalsefalse00falsefalsefalse30falsefalsefalse00falsefalsefalse31falsefalsefalse00falsefalsefalse32falsefalsefalse00falsefalsefalse33falsefalsefalse00falsefalsefalse34falsefalsefalse00falsefalsefalse35falsefalsefalse00falsefalsefalse36falsefalsefalse00falsefalsefalse37falsefalsefalse00falsefalsefalse38falsefalsefalse00falsefalsefalse39falsefalsefalse00falsefalsefalse40falsefalsefalse00falsefalsefalse41falsefalsefalse00falsefalsefalse42falsefalsefalse00falsefalsefalse43falsefalsefalse00falsefalsefalse44falsefalsefalse00falsefalsefalse45falsefalsefalse00falsefalsefalse46falsefalsefalse00falsefalsefalse47falsefalsefalse00falsefalsefalse48falsefalsefalse00falsefalsefalse49falsefalsefalse00falsefalsefalse50falsefalsefalse00falsefalsefalse51falsefalsefalse00falsefalsefalse52falsefalsefalse00falsefalsefalse53falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryFair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G -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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph a -Clause 1 -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 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959 false2Fair Value, Liabilities5false 4invest_DerivativeNotionalAmountinvest_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalse9falsefalsefalse00falsefalsefalse10falsefalsefalse00falsefalsefalse11falsefalsefalse00falsefalsefalse12falsefalsefalse00falsefalsefalse13falsefalsefalse00falsefalsefalse14falsefalsefalse00falsefalsefalse15falsefalsefalse00falsefalsefalse16falsefalsefalse00falsefalsefalse17falsefalsefalse00falsefalsefalse18falsefalsefalse00falsefalsefalse19falsefalsefalse00falsefalsefalse20falsefalsefalse00falsefalsefalse21falsefalsefalse00falsefalsefalse22falsefalsefalse00falsefalsefalse23falsefalsefalse00falsefalsefalse24falsefalsefalse00falsefalsefalse25falsefalsefalse00falsefalsefalse26falsefalsefalse00falsefalsefalse27falsefalsefalse00falsefalsefalse28falsefalsefalse00falsefalsefalse29falsefalsefalse00falsefalsefalse30falsefalsefalse00falsefalsefalse31falsefalsefalse00falsefalsefalse32falsefalsefalse00falsefalsefalse33falsefalsefalse00falsefalsefalse34falsefalsefalse00falsefalsefalse35falsefalsefalse00falsefalsefalse36falsefalsefalse00falsefalsefalse37falsefalsefalse00falsefalsefalse38falsefalsefalse00falsefalsefalse39truefalsefalse308000000308.0falsefalsefalse40truefalsefalse165000000165.0falsefalsefalse41truefalsefalse266500000266.5falsefalsefalse42truefalsefalse155200000155.2falsefalsefalse43truefalsefalse333000000333.0falsefalsefalse44truefalsefalse155100000155.1falsefalsefalse45truefalsefalse18220000001822.0falsefalsefalse46truefalsefalse137800000137.8falsefalsefalse47truefalsefalse1000000.1falsefalsefalse48truefalsefalse1000000010.0falsefalsefalse49truefalsefalse1390000013.9falsefalsefalse50truefalsefalse100000000100.0falsefalsefalse51truefalsefalse100000000100.0falsefalsefalse52truefalsefalse2500000025.0falsefalsefalse53truefalsefalse30000003.0falsefalsefalsexbrli:monetaryItemTypemonetaryAggregate notional amount specified by the derivative(s). Expressed as an absolute value.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B false2Notional Units6false 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net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5618551-113959 false2Net income (loss) from derivative instruments7false 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the number of swap contracts entered into by the entity with a third- party in order to purchase protection against its construction from Japan-based wind and flood exposures.No definition available.false256Number of swaps entered into by the entity8false 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the fixed-rate payment made by the entity related to a swap derivative.No definition available.false2Fixed-rate payment on swap9false 4mrh_DerivativeSwapMaximumRecoverymrh_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalse9falsefalsefalse00falsefalsefalse10falsefalsefalse00falsefalsefalse11falsefalsefalse00falsefalsefalse12falsefalsefalse00falsefalsefalse13falsefalsefalse00falsefalsefalse14falsefalsefalse00falsefalsefalse15falsefalsefalse00falsefalsefalse16falsefalsefalse00falsefalsefalse17falsefalsefalse00falsefalsefalse18falsefalsefalse00falsefalsefalse19falsefalsefalse00falsefalsefalse20falsefalsefalse00falsefalsefalse21falsefalsefalse00falsefalsefalse22falsefalsefalse00falsefalsefalse23falsefalsefalse00falsefalsefalse24falsefalsefalse00falsefalsefalse25falsefalsefalse00falsefalsefalse26falsefalsefalse00falsefalsefalse27falsefalsefalse00falsefalsefalse28falsefalsefalse00falsefalsefalse29falsefalsefalse00falsefalsefalse30falsefalsefalse00falsefalsefalse31falsefalsefalse00falsefalsefalse32falsefalsefalse00falsefalsefalse33falsefalsefalse00falsefalsefalse34falsefalsefalse00falsefalsefalse35falsefalsefalse00falsefalsefalse36truefalsefalse30000003.0falsefalsefalse37truefalsefalse50000005.0falsefalsefalse38truefalsefalse50000005.0falsefalsefalse39falsefalsefalse00falsefalsefalse40falsefalsefalse00falsefalsefalse41falsefalsefalse00falsefalsefalse42falsefalsefalse00falsefalsefalse43falsefalsefalse00falsefalsefalse44falsefalsefalse00falsefalsefalse45falsefalsefalse00falsefalsefalse46falsefalsefalse00falsefalsefalse47falsefalsefalse00falsefalsefalse48falsefalsefalse00falsefalsefalse49falsefalsefalse00falsefalsefalse50falsefalsefalse00falsefalsefalse51falsefalsefalse00falsefalsefalse52falsefalsefalse00falsefalsefalse53falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents the maximum recovery under each individual derivative swap.No definition available.false2Maximum recovery under each swap10false 4mrh_DerivativeSwapAggregateMaximumRecoverymrh_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalse9falsefalsefalse00falsefalsefalse10falsefalsefalse00falsefalsefalse11falsefalsefalse00falsefalsefalse12falsefalsefalse00falsefalsefalse13falsefalsefalse00falsefalsefalse14falsefalsefalse00falsefalsefalse15falsefalsefalse00falsefalsefalse16falsefalsefalse00falsefalsefalse17falsefalsefalse00falsefalsefalse18falsefalsefalse00falsefalsefalse19falsefalsefalse00falsefalsefalse20falsefalsefalse00falsefalsefalse21falsefalsefalse00falsefalsefalse22falsefalsefalse00falsefalsefalse23falsefalsefalse00falsefalsefalse24falsefalsefalse00falsefalsefalse25falsefalsefalse00falsefalsefalse26falsefalsefalse00falsefalsefalse27falsefalsefalse00falsefalsefalse28falsefalsefalse00falsefalsefalse29falsefalsefalse00falsefalsefalse30falsefalsefalse00falsefalsefalse31falsefalsefalse00falsefalsefalse32falsefalsefalse00falsefalsefalse33falsefalsefalse00falsefalsefalse34falsefalsefalse00falsefalsefalse35falsefalsefalse00falsefalsefalse36falsefalsefalse00falsefalsefalse37truefalsefalse2000000020.0USD$falsetruefalse38falsefalsefalse00falsefalsefalse39falsefalsefalse00falsefalsefalse40falsefalsefalse00falsefalsefalse41falsefalsefalse00falsefalsefalse42falsefalsefalse00falsefalsefalse43falsefalsefalse00falsefalsefalse44falsefalsefalse00falsefalsefalse45falsefalsefalse00falsefalsefalse46falsefalsefalse00falsefalsefalse47falsefalsefalse00falsefalsefalse48falsefalsefalse00falsefalsefalse49falsefalsefalse00falsefalsefalse50falsefalsefalse00falsefalsefalse51falsefalsefalse00falsefalsefalse52falsefalsefalse00falsefalsefalse53falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents the aggregate maximum recovery for the derivative swaps when more than one entered.No definition available.false2Aggregate maximum recovery under swapsfalseDerivative Instruments (Details) (USD $)HundredThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.montpelierre.bm/role/DisclosureDerivativeInstrumentsDetails5310