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Note 5 - Investments Net Unrealized Gains (Losses) on Investment Securities (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2020 | Mar. 31, 2019
Gain (Loss) on Securities [Line Items] |  |
Net changes in unrealized gains (losses) on investments | $ (25,250) | $ 16,506
Trading Securities |  |
Gain (Loss) on Securities [Line Items] |  |
Trading Securities, Change in Unrealized Holding Gain (Loss) | (2,034) | 8,587
Equity securities |  |
Gain (Loss) on Securities [Line Items] |  |
Equity Securities, Change in Unrealized Holding Gain (Loss) | (24,020) | 7,919
Other investments |  |
Gain (Loss) on Securities [Line Items] |  |
Other Investments, Change in Unrealized Holding Gain (Loss) | $ 804 | $ 0

X
- Definition Amount of unrealized holding gain (loss) recognized in the income statement for investments in equity securities and securities classified as trading. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of the change in unrealized holding gain (loss) recognized in the income statement for investments in equity securities. + References No definition available. + Details
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Namespace Prefix: | rdn_
Data Type: | xbrli:monetaryItemType
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- Definition Other Investments, Change in Unrealized Holding Gain (Loss) + References No definition available. + 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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- Definition Amount of unrealized holding gain (loss) recognized in the income statement for investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading. + References No definition available. + Details
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X
- Details
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X
- Details
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