XML 72 R57.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | $ 3,380,642 | $ 3,403,822
Fair value of liabilities measured on a recurring basis | 301,785 | 294,219
Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 478,197 | 742,886
Fair value of liabilities measured on a recurring basis | 260 | 194
Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 2,892,014 | 2,649,217
Fair value of liabilities measured on a recurring basis | 301,525 | 294,025
Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 10,431 | 11,719
Fair value of liabilities measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | US Treasury and Government [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 22,507 | 16,108
Fixed Maturity Securities [Member] | US Treasury and Government [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 22,507 | 16,108
Fixed Maturity Securities [Member] | US Treasury and Government [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | US Treasury and Government [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | US States and Political Subdivisions Debt Securities [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 2,505,040 | 2,275,455
Fixed Maturity Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 2,505,040 | 2,275,455
Fixed Maturity Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 49,838 | 47,691
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 49,838 | 47,691
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 243,372 | 256,930
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 243,372 | 256,930
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 50,548 | 22,216
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 50,548 | 22,216
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 8,698 |
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 |
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 8,698 |
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 |
Equity Securities [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 280,263 | 372,598
Equity Securities [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 280,263 | 372,598
Equity Securities [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Equity Securities [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 24,668 | 28,563
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 24,668 | 28,563
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Equity Securities [Member] | Private Equity Funds [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 10,431 | 11,719
Equity Securities [Member] | Private Equity Funds [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Equity Securities [Member] | Private Equity Funds [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Equity Securities [Member] | Private Equity Funds [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 10,431 | 11,719
Short-term Investments [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 79,841 | 88,361
Short-term Investments [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 69,991 | 69,999
Short-term Investments [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 9,850 | 18,362
Short-term Investments [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Money Market Funds [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 105,436 | 284,181
Money Market Funds [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 105,436 | 284,181
Money Market Funds [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Money Market Funds [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of assets measured on a recurring basis | 0 | 0
Total Return Swap [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 11,525 | 4,025
Total Return Swap [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 0 | 0
Total Return Swap [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 11,525 | 4,025
Total Return Swap [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 0 | 0
Equity Contract [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 260 | 194
Equity Contract [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 260 | 194
Equity Contract [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 0 | 0
Equity Contract [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 0 | 0
Secured Debt [Member] | Borrowings [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 140,000 | 140,000
Secured Debt [Member] | Borrowings [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 0 | 0
Secured Debt [Member] | Borrowings [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 140,000 | 140,000
Secured Debt [Member] | Borrowings [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 0 | 0
Unsecured Debt [Member] | Borrowings [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 150,000 | 150,000
Unsecured Debt [Member] | Borrowings [Member] | Level 1 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 0 | 0
Unsecured Debt [Member] | Borrowings [Member] | Level 2 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | 150,000 | 150,000
Unsecured Debt [Member] | Borrowings [Member] | Level 3 [Member] |  |
Fair Value Measurement [Line Items] |  |
Fair value of liabilities measured on a recurring basis | $ 0 | $ 0

X
- Definition Fair Value Measurement [Line Items] + References No definition available. + Details
Name: | mcy_FairValueMeasurementLineItems
Namespace Prefix: | mcy_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a recurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References No definition available. + Details
Name: | us-gaap_AssetsFairValueDisclosureRecurring
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Aggregation of the liabilities reported on the balance sheet measured at fair value on a recurring basis by the entity. + References No definition available. + Details
Name: | us-gaap_LiabilitiesFairValueDisclosureRecurring
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CollateralizedAutoLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_NonredeemablePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_PrivateEquityFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_TotalReturnSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_EquityContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EligibleItemOrGroupForFairValueOptionAxis=us-gaap_BorrowingsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |