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Investments Fair Value Measurements (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis $ 71,589,000us-gaap_AssetsFairValueDisclosure [1] $ 85,946,000us-gaap_AssetsFairValueDisclosure  
Short-term interest rate reset dates of auction rate note securities less than ninety days    
Auction rate note securities with contractual maturities excess of ten years    
Period for principal repayments 33 years    
Reset period for the securities held seven or twenty eight days    
Comprehensive income (loss) net of tax due to auction rate notes 237,000us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax 212,000us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax 355,000us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax
Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 4,725,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember		 [2] 16,945,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember		 [2]  
Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 43,262,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 [3] 36,957,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		  
Commercial Paper [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 14,977,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember		 [3] 13,993,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember		  
Auction Rate Notes [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 1,436,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		 [1] 4,195,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		  
Interest rate, percent in excess of one month LIBOR 1.50%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		    
Comprehensive income (loss) before tax due to auction rate notes (100,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		    
Comprehensive income (loss) net of tax due to auction rate notes (100,000)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		    
Municipal Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 5,194,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_MunicipalBondsMember		 [3] 13,856,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_MunicipalBondsMember		  
U.S. Government Agencies Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 1,995,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember		 [3]    
Quoted Prices in Active Markets for Identical Assets Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 4,725,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 [1] 16,945,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 [1]  
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 4,725,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember		 [2] 16,945,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember		 [2]  
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 [3] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 [3]  
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Commercial Paper [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember		 [3] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember		 [3]  
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Auction Rate Notes [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		 [1] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		 [1]  
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Municipal Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_MunicipalBondsMember		 [3] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_MunicipalBondsMember		 [3]  
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | U.S. Government Agencies Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember		 [3]    
Significant Other Observable Inputs Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 65,428,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 [1] 64,806,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 [1]  
Significant Other Observable Inputs Level 2 [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember		 [2] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember		 [2]  
Significant Other Observable Inputs Level 2 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 43,262,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 [3] 36,957,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 [3]  
Significant Other Observable Inputs Level 2 [Member] | Commercial Paper [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 14,977,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember		 [3] 13,993,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember		 [3]  
Significant Other Observable Inputs Level 2 [Member] | Auction Rate Notes [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		 [1] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		 [1]  
Significant Other Observable Inputs Level 2 [Member] | Municipal Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 5,194,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_MunicipalBondsMember		 [3] 13,856,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_MunicipalBondsMember		 [3]  
Significant Other Observable Inputs Level 2 [Member] | U.S. Government Agencies Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 1,995,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember		 [3]    
Significant Unobservable Inputs Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 1,436,000us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 4,195,000us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		  
Transfers in and/or out of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		    
Total gains, before tax 441,000mcrl_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossBeforeTax
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		    
Settlements (3,200,000)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		    
Financial assets and liabilities measured at fair value on a recurring basis 1,436,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 [1] 4,195,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 [1]  
Significant Unobservable Inputs Level 3 [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember		 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MoneyMarketFundsMember		 [2]  
Significant Unobservable Inputs Level 3 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 [3] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 [3]  
Significant Unobservable Inputs Level 3 [Member] | Commercial Paper [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember		 [3] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialPaperNotIncludedWithCashAndCashEquivalentsMember		 [3]  
Significant Unobservable Inputs Level 3 [Member] | Auction Rate Notes [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 1,436,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		 [1] 4,195,000us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AuctionRateSecuritiesMember		 [1]  
Significant Unobservable Inputs Level 3 [Member] | Municipal Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_MunicipalBondsMember		 [3] 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_MunicipalBondsMember		 [3]  
Significant Unobservable Inputs Level 3 [Member] | U.S. Government Agencies Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial assets and liabilities measured at fair value on a recurring basis $ 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember		 [3]    
[1] Included in long-term investments
[2] Included in cash and cash equivalents
[3] Included in short-term investments