XML 107 R89.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Loss And Loss Adjustment Expense Reserves - Average Annual Percentage Payout of Incurred Claims by Age (Details) | Dec. 31, 2023
--- | ---
Property insurance product line, automobile |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration insurance contracts, historical claims duration, year one | 59.10%
Short-duration insurance contracts, historical claims duration, year two | 19.00%
Short-duration insurance contracts, historical claims duration, year three | 9.40%
Short-duration insurance contracts, historical claims duration, year four | 5.70%
Short-duration insurance contracts, historical claims duration, year five | 3.10%
Short-duration insurance contracts, historical claims duration, year six | 1.40%
Short-duration insurance contracts, historical claims duration, year seven | 0.60%
Short-duration insurance contracts, historical claims duration, year eight | 0.30%
Short-duration insurance contracts, historical claims duration, year nine | 0.10%
Short-duration insurance contracts, historical claims duration, year ten | 0.10%
Property insurance product line, homeowners' |
Short-duration Insurance Contracts, Historical Claims Duration [Line Items] |
Short-duration insurance contracts, historical claims duration, year one | 66.80%
Short-duration insurance contracts, historical claims duration, year two | 23.00%
Short-duration insurance contracts, historical claims duration, year three | 4.10%
Short-duration insurance contracts, historical claims duration, year four | 2.40%
Short-duration insurance contracts, historical claims duration, year five | 1.50%
Short-duration insurance contracts, historical claims duration, year six | 0.80%
Short-duration insurance contracts, historical claims duration, year seven | 0.60%
Short-duration insurance contracts, historical claims duration, year eight | 0.30%
Short-duration insurance contracts, historical claims duration, year nine | 0.40%
Short-duration insurance contracts, historical claims duration, year ten | 0.10%

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of average annual payout, after reinsurance, in the eighth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearEight
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the fifth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearFive
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the fourth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearFour
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the ninth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearNine
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the first year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearOne
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the seventh year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearSeven
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the sixth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearSix
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the tenth year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearTen
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the third year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearThree
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of average annual payout, after reinsurance, in the second year after a claim is incurred, beginning with the earliest accident year disclosed for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4G -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4G + Details
Name: | us-gaap_ShortdurationInsuranceContractsHistoricalClaimsDurationYearTwo
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | srt_ProductOrServiceAxis=mcy_PropertyInsuranceProductLineAutomobileMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=mcy_PropertyInsuranceProductLineHomeownersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |