Income Taxes - Taxable income and Taxable Net Realized Gains Losses (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions  | 
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2024  | 
Jun. 30, 2023  | 
Jun. 30, 2024  | 
Jun. 30, 2023  | 
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| Income Tax Disclosure [Abstract] | ||||
| Taxable income | $ 75.9 | $ 60.9 | $ 154.2 | $ 125.0 | 
| Taxable income, per share (in dollars per share) | $ 0.47 | $ 0.43 | $ 0.97 | $ 0.90 | 
| Taxable net realized gains (losses) | $ 3.5 | $ 20.2 | $ 9.4 | $ 27.4 | 
| Taxable net realized gains, per share (in dollars per share) | $ 0.02 | $ 0.14 | $ 0.06 | $ 0.20 | 
| Weighted average shares outstanding (in shares) | 160,748 | 141,390 | 159,096 | 138,338 | 
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- Definition Taxable income per share. No definition available. 
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- Definition Taxable net income (loss). No definition available. 
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- Definition Taxable net realized gain loss. No definition available. 
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- Definition Taxable net realized gain (loss) per share. No definition available. 
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- References No definition available. 
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- Definition Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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