XML 50 R37.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Fair Value Measurement (Summary Of Changes In Fair Value Of Level 3 Financial Assets And Financial Liabilities Held At Fair Value) (Details) - Private Equity Funds [Member] - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Beginning Balance | $ 8,764 | $ 8,972 | $ 9,068 | $ 10,431
Realized (losses) gains included in earnings | (80) | 564 | (384) | (895)
Ending Balance | 8,684 | 9,536 | 8,684 | 9,536
The amount of total (losses) gains for the period included in earnings attributable to assets still held at September 30 | $ (80) | $ 564 | $ (384) | $ (895)

X
- Definition Amount of total losses gains for period included in earnings attributable to assets still held + References No definition available. + Details
Name: | mcy_AmountOfTotalLossesGainsForPeriodIncludedInEarningsAttributableToAssetsStillHeld
Namespace Prefix: | mcy_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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