XML 47 R31.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2021
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,
| 2021 |  | 2020 |  | 2019
| (Amounts in millions)
Deferred policy acquisition cost amortization | $ | 633.4 |  |  | $ | 627.8 |  |  | $ | 602.1 |
Net advertising expense | 50.1 |  |  | 37.7 |  |  | 42.2 |
Effects of Reinsurance | The effect of reinsurance on property and casualty premiums written and earned was as follows:
| Year Ended December 31,
| 2021 |  | 2020 |  | 2019
| (Amounts in thousands)
Premiums Written |  |  |  |  |
Direct | $ | 3,877,476 |  |  | $ | 3,624,965 |  |  | $ | 3,742,627 |
Ceded | (65,521) |  |  | (50,630) |  |  | (43,785) |
Assumed | 13,361 |  |  | 8,012 |  |  | 919 |
Net | $ | 3,825,316 |  |  | $ | 3,582,347 |  |  | $ | 3,699,761 |
Premiums Earned |  |  |  |  |
Direct | $ | 3,764,626 |  |  | $ | 3,574,898 |  |  | $ | 3,626,857 |
Ceded | (65,017) |  |  | (56,212) |  |  | (56,725) |
Assumed | 13,301 |  |  | 8,067 |  |  | 910 |
Net | $ | 3,712,910 |  |  | $ | 3,526,753 |  |  | $ | 3,571,042 |
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,
|  | 2021 |  | 2020 |  | 2019
Beginning balance |  | $ | 10,000 |  |  | $ | 1,445 |  |  | 1,458 |
Cumulative effect of adopting ASU 2016-13 |  | — |  |  | 1,855 |  |  | — |
Beginning balance, as adjusted |  | 10,000 |  |  | 3,300 |  |  | 1,458 |
Provision during the period for expected credit losses |  | (893) |  |  | 10,294 |  |  | 6,162 |
Write-off amounts during the period |  | (3,693) |  |  | (4,406) |  |  | (7,000) |
Recoveries during the period of amounts previously written off |  | 586 |  |  | 812 |  |  | 825 |
Ending balance |  | $ | 6,000 |  |  | $ | 10,000 |  |  | $ | 1,445 |
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,
|  | 2021 |  | 2020 |  | 2019
Beginning balance |  | $ | 91 |  |  | $ | — |  |  | $ | — |
Cumulative effect of adopting ASU 2016-13 |  | — |  |  | 159 |  |  | — |
Beginning balance, as adjusted |  | 91 |  |  | 159 |  |  | — |
Provision during the period for expected credit losses |  | (91) |  |  | (68) |  |  | — |
Write-off amounts during the period |  | — |  |  | — |  |  | — |
Recoveries during the period of amounts previously written off |  | — |  |  | — |  |  | — |
Ending balance |  | $ | — |  |  | $ | 91 |  |  | $ | — |

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-types: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 -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 + Details
Name: | us-gaap_ReinsuranceRecoverableAllowanceForCreditLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration