XML 47 R33.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Fair Value of Financial Instruments (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2017
Financial Instruments, Owned, at Fair Value [Abstract] |
Estimated Fair Values of Financial Instruments | The following table presents the fair values of financial instruments:
| December 31,
| 2017 |  | 2016
| (Amounts in thousands)
Assets |  |  |
Investments | $ | 3,732,728 |  |  | $ | 3,547,560 |
Note receivable | 5,565 |  |  | — |
Total return swaps | — |  |  | 667 |
Liabilities |  |  |
Total return swaps | 1,200 |  |  | 765 |
Options sold | 123 |  |  | 20 |
Secured notes | — |  |  | 140,000 |
Unsecured notes | 385,583 |  |  | 180,000 |

X
- Definition Estimated Fair Values of Financial Instruments [Table Text Block] + References No definition available. + Details
Name: | mcy_EstimatedFairValuesOfFinancialInstrumentsTableTextBlock
Namespace Prefix: | mcy_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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