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Unrealized Appreciation (Depreciation) and Realized Gains (Losses) on Investments - Schedule of Unrealized Appreciation (Depreciation) on Investments (Detail) $ in Thousands | 3 Months Ended
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Mar. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items] |
Beginning balance | $ 139,700
Appreciation on investments | 37,797
Depreciation on investments | (40,067)
Losses on investments | 34,747
Ending balance | 172,177
Medallion [Member] |
Debt Securities, Available-for-sale [Line Items] |
Beginning balance | (20,338)
Depreciation on investments | (38,170)
Losses on investments | 34,747
Ending balance | (23,761)
Commercial Loans [Member] |
Debt Securities, Available-for-sale [Line Items] |
Beginning balance | (513)
Depreciation on investments | 18
Ending balance | (495)
Investments in Subsidiaries [Member] |
Debt Securities, Available-for-sale [Line Items] |
Beginning balance | 158,920
Appreciation on investments | 38,795
Ending balance | 197,715
Equity Investments [Member] |
Debt Securities, Available-for-sale [Line Items] |
Beginning balance | 3,121
Appreciation on investments | (998)
Ending balance | 2,123
Investments Other than Securities [Member] |
Debt Securities, Available-for-sale [Line Items] |
Beginning balance | (1,490)
Depreciation on investments | (1,915)
Ending balance | $ (3,405)

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- Definition Appreciation on investment. + References No definition available. + Details
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Period Type: | duration

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- Definition Depreciation on investments + References No definition available. + Details
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- Definition Reverse in unrealized loss on investments. + References No definition available. + Details
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- Definition This element represents the net excess or deficiency of the fair value of an investment (security, contract) over or under its cost (face amount, notional amount), respectively, which excess value or deficiency has not been recognized in earnings of the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=120401592&loc=SL6090603-123010 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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