XML 37 R23.htm IDEA: XBRL DOCUMENT
v3.20.2

Fair Value Option (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2020
Fair Value Option [Abstract] |
Gains And Losses Due To Changes In Fair Value Of Investments | The following table presents gains (losses) due to changes in fair value of investments and the note receivable that are measured at fair value pursuant to application of the fair value option:
| Three Months Ended September 30, |  | Nine Months Ended September 30,
| 2020 |  | 2019 |  | 2020 |  | 2019
| (Amounts in thousands)
Fixed maturity securities | $ | 21,112 |  |  | $ | 22,403 |  |  | $ | 21,350 |  |  | $ | 110,559 |
Equity securities | 37,734 |  |  | 1,928 |  |  | (36,699) |  |  | 66,976 |
Short-term investments | (20) |  |  | (326) |  |  | (18) |  |  | 898 |
Total investments | $ | 58,826 |  |  | $ | 24,005 |  |  | $ | (15,367) |  |  | $ | 178,433 |
Note receivable | 39 |  |  | 18 |  |  | 71 |  |  | 96 |
Total gains (losses) | $ | 58,865 |  |  | $ | 24,023 |  |  | $ | (15,296) |  |  | $ | 178,529 |

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: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration