XML 52 R36.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2024
Accounting Policies [Abstract] |
Summary of Deferred Policy Acquisition Cost Amortization and Net Advertising Expense | The table below presents a summary of deferred policy acquisition cost amortization and net advertising expense:
| Year Ended December 31,
| 2024 |  | 2023 |  | 2022
| (Amounts in millions)
Deferred policy acquisition cost amortization | $ | 858.3 |  |  | $ | 708.5 |  |  | $ | 654.6 |
Net advertising expense | 20.8 |  |  | 8.9 |  |  | 11.8 |
Effects of Reinsurance | The effect of reinsurance on property and casualty premiums written and earned was as follows:
| Year Ended December 31,
| 2024 |  | 2023 |  | 2022
| (Amounts in thousands)
Premiums Written |  |  |  |  |
Direct | $ | 5,474,292 |  |  | $ | 4,531,942 |  |  | $ | 4,018,057 |
Ceded | (138,015) |  |  | (109,644) |  |  | (81,256) |
Assumed | 15,489 |  |  | 15,353 |  |  | 10,743 |
Net | $ | 5,351,766 |  |  | $ | 4,437,651 |  |  | $ | 3,947,544 |
Premiums Earned |  |  |  |  |
Direct | $ | 5,167,342 |  |  | $ | 4,339,333 |  |  | $ | 3,993,771 |
Ceded | (136,698) |  |  | (109,445) |  |  | (80,950) |
Assumed | 15,455 |  |  | 15,481 |  |  | 10,821 |
Net | $ | 5,046,099 |  |  | $ | 4,245,369 |  |  | $ | 3,923,642 |
Premium Receivable, Allowance for Credit Loss | The following table presents a summary of changes in allowance for credit losses on premiums receivable:
|  | Year Ended December 31,
|  | 2024 |  | 2023 |  | 2022
|  | (Amounts in thousands)
Beginning balance |  | $ | 5,300 |  |  | $ | 5,800 |  |  | $ | 6,000 |
Provision during the period for expected credit losses |  | 3,752 |  |  | 2,819 |  |  | 4,213 |
Write-off amounts during the period |  | (3,559) |  |  | (3,879) |  |  | (5,027) |
Recoveries during the period of amounts previously written off |  | 907 |  |  | 560 |  |  | 614 |
Ending balance |  | $ | 6,400 |  |  | $ | 5,300 |  |  | $ | 5,800 |
Reinsurance Recoverable, Allowance for Credit Loss | The following table presents a summary of changes in allowance for credit losses on reinsurance recoverables:
|  | Year Ended December 31,
|  | 2024 |  | 2023 |  | 2022
|  | (Amounts in thousands)
Beginning balance |  | $ | 12 |  |  | $ | — |  |  | $ | — |
Provision during the period for expected credit losses |  | (12) |  |  | 12 |  |  | — |
Write-off amounts during the period |  | — |  |  | — |  |  | — |
Recoveries during the period of amounts previously written off |  | — |  |  | — |  |  | — |
Ending balance |  | $ | — |  |  | $ | 12 |  |  | $ | — |

X
- Definition Summary of Deferred Policy Acquisition Cost Amortization and Net Advertising Expense [Table Text Block] + References No definition available. + Details
Name: | mcy_SummaryofDeferredPolicyAcquisitionCostAmortizationandNetAdvertisingExpenseTableTextBlock
Namespace Prefix: | mcy_
Data Type: | dtr-types1:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the effects of reinsurance, for example, but not limited to, disclosure of direct, assumed, and ceded insurance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -SubTopic 605 -Topic 944 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479032/944-605-50-1 + Details
Name: | us-gaap_EffectsOfReinsuranceTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of allowance for credit loss on premium receivable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 + Details
Name: | us-gaap_PremiumReceivableAllowanceForCreditLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of allowance for credit loss on reinsurance recoverable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 + Details
Name: | us-gaap_ReinsuranceRecoverableAllowanceForCreditLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration