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Investments Investments - Distribution of Commercial Mortgage and Middle Market Loans (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Commercial mortgage loans |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 163.6 | $ 156.6
Concentration risk percentage | 100.00% | 100.00%
Middle market loans |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 112.1 | $ 111.7
Concentration risk percentage | 100.00% | 100.00%
Investment, Net Carrying Value | Commercial mortgage loans | Product Concentration Risk | Office building |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 33.9 | $ 21.9
Concentration risk percentage | 20.70% | 14.00%
Investment, Net Carrying Value | Commercial mortgage loans | Product Concentration Risk | Apartment |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 80.7 | $ 48.3
Concentration risk percentage | 49.30% | 30.80%
Investment, Net Carrying Value | Commercial mortgage loans | Product Concentration Risk | Hotel |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 20.4 | $ 47.7
Concentration risk percentage | 12.50% | 30.40%
Investment, Net Carrying Value | Commercial mortgage loans | Product Concentration Risk | Other commercial |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 28.6 | $ 17.0
Concentration risk percentage | 17.50% | 10.90%
Investment, Net Carrying Value | Commercial mortgage loans | Product Concentration Risk | Retail |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 0.0 | $ 15.2
Concentration risk percentage | 0.00% | 9.70%
Investment, Net Carrying Value | Commercial mortgage loans | Product Concentration Risk | Industrial |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 0.0 | $ 6.5
Concentration risk percentage | 0.00% | 4.20%
Investment, Net Carrying Value | Middle market loans | Product Concentration Risk | Materials |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 28.0 | $ 29.5
Concentration risk percentage | 24.90% | 26.40%
Investment, Net Carrying Value | Middle market loans | Product Concentration Risk | Financials |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 27.1 | $ 22.2
Concentration risk percentage | 24.20% | 19.80%
Investment, Net Carrying Value | Middle market loans | Product Concentration Risk | Industrials |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 17.3 | $ 18.9
Concentration risk percentage | 15.50% | 17.00%
Investment, Net Carrying Value | Middle market loans | Product Concentration Risk | Consumer discretionary |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 13.7 | $ 14.2
Concentration risk percentage | 12.20% | 12.70%
Investment, Net Carrying Value | Middle market loans | Product Concentration Risk | Health care |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 7.5 | $ 8.2
Concentration risk percentage | 6.70% | 7.40%
Investment, Net Carrying Value | Middle market loans | Product Concentration Risk | Energy |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 7.3 | $ 7.4
Concentration risk percentage | 6.50% | 6.60%
Investment, Net Carrying Value | Middle market loans | Product Concentration Risk | Consumer staples |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 6.4 | $ 6.4
Concentration risk percentage | 5.70% | 5.70%
Investment, Net Carrying Value | Middle market loans | Product Concentration Risk | Information technology |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 4.8 | $ 4.9
Concentration risk percentage | 4.30% | 4.40%
U.S. | Investment, Net Carrying Value | Commercial mortgage loans | Geographic Concentration Risk |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 122.7 | $ 85.5
Concentration risk percentage | 75.00% | 54.60%
U.S. | Investment, Net Carrying Value | Middle market loans | Geographic Concentration Risk |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 91.8 | $ 91.8
Concentration risk percentage | 81.90% | 82.20%
International | Investment, Net Carrying Value | Commercial mortgage loans | Geographic Concentration Risk |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 40.9 | $ 71.1
Concentration risk percentage | 25.00% | 45.40%
International | Investment, Net Carrying Value | Middle market loans | Geographic Concentration Risk |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |
Fair market value, trading | $ 20.3 | $ 19.9
Concentration risk percentage | 18.10% | 17.80%

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