v3.8.0.1

Investments - Credit Ratings (Details) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Schedule of Fixed Maturities Table [Line Items] |  |  |  |  |
OTTI | $ 0 | $ 0 | $ 0 | $ 0 |
Fixed Maturities, Amortized cost | 4,963,364,000 |  | 4,963,364,000 |  | $ 4,757,854,000
Fixed Maturities, Fair value | $ 5,036,693,000 |  | $ 5,036,693,000 |  | $ 4,737,801,000
Fixed maturities, % of Total fair value | 100.00% |  | 100.00% |  | 100.00%
AAA [Member] |  |  |  |  |
Schedule of Fixed Maturities Table [Line Items] |  |  |  |  |
Fixed Maturities, Amortized cost | $ 169,514,000 |  | $ 169,514,000 |  | $ 170,515,000
Fixed Maturities, Fair value | $ 173,589,000 |  | $ 173,589,000 |  | $ 171,090,000
Fixed maturities, % of Total fair value | 3.40% |  | 3.40% |  | 3.60%
AA Plus, AA, AA Minus [Member] |  |  |  |  |
Schedule of Fixed Maturities Table [Line Items] |  |  |  |  |
Fixed Maturities, Amortized cost | $ 238,268,000 |  | $ 238,268,000 |  | $ 238,315,000
Fixed Maturities, Fair value | $ 244,507,000 |  | $ 244,507,000 |  | $ 237,169,000
Fixed maturities, % of Total fair value | 4.90% |  | 4.90% |  | 5.00%
A Plus, A, A Minus [Member] |  |  |  |  |
Schedule of Fixed Maturities Table [Line Items] |  |  |  |  |
Fixed Maturities, Amortized cost | $ 1,395,001,000 |  | $ 1,395,001,000 |  | $ 1,386,023,000
Fixed Maturities, Fair value | $ 1,421,504,000 |  | $ 1,421,504,000 |  | $ 1,374,860,000
Fixed maturities, % of Total fair value | 28.30% |  | 28.30% |  | 29.00%
BBB Plus, BBB, BBB Minus [Member] |  |  |  |  |
Schedule of Fixed Maturities Table [Line Items] |  |  |  |  |
Fixed Maturities, Amortized cost | $ 1,093,491,000 |  | $ 1,093,491,000 |  | $ 1,053,529,000
Fixed Maturities, Fair value | $ 1,125,119,000 |  | $ 1,125,119,000 |  | $ 1,047,376,000
Fixed maturities, % of Total fair value | 22.30% |  | 22.30% |  | 22.20%
BB Plus or Lower [Member] |  |  |  |  |
Schedule of Fixed Maturities Table [Line Items] |  |  |  |  |
Fixed Maturities, Amortized cost | $ 57,251,000 |  | $ 57,251,000 |  | $ 165,768,000
Fixed Maturities, Fair value | $ 60,236,000 |  | $ 60,236,000 |  | $ 167,753,000
Fixed maturities, % of Total fair value | 1.20% |  | 1.20% |  | 3.50%
U.S. treasury bonds [Member] |  |  |  |  |
Schedule of Fixed Maturities Table [Line Items] |  |  |  |  |
Fixed Maturities, Amortized cost | $ 5,194,000 |  | $ 5,194,000 |  | $ 5,186,000
Fixed Maturities, Fair value | $ 5,336,000 |  | $ 5,336,000 |  | $ 5,413,000
Fixed maturities, % of Total fair value | 0.10% |  | 0.10% |  | 0.10%
U.S. agency bonds [Member] |  |  |  |  |
Schedule of Fixed Maturities Table [Line Items] |  |  |  |  |
Fixed Maturities, Amortized cost | $ 2,004,645,000 |  | $ 2,004,645,000 |  | $ 1,738,518,000
Fixed Maturities, Fair value | $ 2,006,402,000 |  | $ 2,006,402,000 |  | $ 1,734,140,000
Fixed maturities, % of Total fair value | 39.80% |  | 39.80% |  | 36.60%

X
- Definition Fixed Maturities, Amortized Cost Basis + References No definition available. + Details
Name: | mhld_FixedMaturitiesAmortizedCostBasis
Namespace Prefix: | mhld_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fixed Maturities, Fair Value + References No definition available. + Details
Name: | mhld_FixedMaturitiesFairValue
Namespace Prefix: | mhld_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fixed Maturities, Percent of Total Fair Value + References No definition available. + Details
Name: | mhld_FixedMaturitiesPercentofTotalFairValue
Namespace Prefix: | mhld_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition [Line Items] for Schedule of Fixed Maturities Table [Table] + References No definition available. + Details
Name: | mhld_ScheduleofFixedMaturitiesTableLineItems
Namespace Prefix: | mhld_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_CreditRatingStandardPoorsAxis=us-gaap_StandardPoorsAAARatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingStandardPoorsAxis=mhld_StandardPoorsAaPlusAaAaMinusRatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingStandardPoorsAxis=mhld_StandardPoorsSingleaPlusSingleaAndSingleaMinusMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingStandardPoorsAxis=mhld_StandardPoorsBbbPlusBbbBbbMinusRatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingStandardPoorsAxis=mhld_StandardPoorsBbPlusOrLowerRatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |