XML 35 R23.htm IDEA: XBRL DOCUMENT
v3.22.2.2

Fair Value Option (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2022
Fair Value Option [Abstract] |
Gains And Losses Due To Changes In Fair Value Of Investments | The following table presents gains or losses recognized due to changes in fair value of financial instruments pursuant to application of the fair value option:
| Three Months Ended September 30, |  | Nine Months Ended September 30,
| 2022 |  | 2021 |  | 2022 |  | 2021
| (Amounts in thousands)
Fixed maturity securities | $ | (83,257) |  |  | $ | (26,120) |  |  | $ | (329,458) |  |  | $ | (21,729) |
Equity securities | (45,779) |  |  | (19,884) |  |  | (220,469) |  |  | 47,057 |
Short-term investments | 1,817 |  |  | (170) |  |  | 152 |  |  | (161) |
Total investments | $ | (127,219) |  |  | $ | (46,174) |  |  | $ | (549,775) |  |  | $ | 25,167 |
Note receivable | — |  |  | 43 |  |  | — |  |  | 15 |
Total (losses) gains | $ | (127,219) |  |  | $ | (46,131) |  |  | $ | (549,775) |  |  | $ | 25,182 |

X
- Definition Fair Value Option [Abstract] + References No definition available. + Details
Name: | mcy_FairValueOptionAbstract
Namespace Prefix: | mcy_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of unrealized gains and losses on investments. + References No definition available. + Details
Name: | us-gaap_UnrealizedGainLossOnInvestmentsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration