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Investment Securities (Fair Value Measurement by Level) (Details) $ in Millions | Mar. 31, 2019 USD ($) Investment | Dec. 31, 2018 USD ($) Investment | Mar. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
--- | --- | --- | --- | ---
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | $ 2,534.6 | $ 2,328.7 | $ 2,532.5 | $ 3,208.3
Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 799.3 | 842.6 | 874.3 | 890.4
Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | $ 1,237.7 | $ 1,160.5 | 1,405.1 | 2,105.4
Common Stock |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Number of hedge funds | Investment | 2 | 2 |  |
Debt securities issued by corporations |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | $ 544.8 | $ 510.5 |  |
Mortgage-backed and asset-backed securities |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 148.8 | 133.5 |  |
Mortgage-backed and asset-backed securities | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 148.8 | 133.5 |  |
Mortgage-backed and asset-backed securities | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Other long-term investments | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 275.1 | 138.7 | 113.4 | 77.2
Hedge and private equity funds included in other long-term investments | NAV |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 222.5 | 186.9 | 139.7 | 135.3
Fair value measured on a recurring basis |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 2,804.4 | 2,542.9 |  |
Fair value measured on a recurring basis | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 1,048.3 | 1,047.0 |  |
Fair value measured on a recurring basis | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 1,258.5 | 1,170.3 |  |
Fair value measured on a recurring basis | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 275.1 | 138.7 |  |
Fair value measured on a recurring basis | U.S. Government and agency obligations |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 153.0 | 153.2 |  |
Fair value measured on a recurring basis | U.S. Government and agency obligations | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 153.0 | 153.2 |  |
Fair value measured on a recurring basis | U.S. Government and agency obligations | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | U.S. Government and agency obligations | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 544.8 | 510.5 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 544.8 | 510.5 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Financials |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 139.7 | 143.4 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Financials | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Financials | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 139.7 | 143.4 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Financials | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Health Care |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 74.7 | 55.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Health Care | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Health Care | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 74.7 | 55.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Health Care | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Energy |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 66.0 | 57.6 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Energy | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Energy | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 66.0 | 57.6 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Energy | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Consumer |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 61.0 | 68.5 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Consumer | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Consumer | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 61.0 | 68.5 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Consumer | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Industrial |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 57.0 | 47.6 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Industrial | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Industrial | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 57.0 | 47.6 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Industrial | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Technology |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 55.0 | 60.5 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Technology | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Technology | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 55.0 | 60.5 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Technology | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Communications |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 40.4 | 31.8 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Communications | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Communications | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 40.4 | 31.8 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Communications | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Utilities |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 28.5 | 19.8 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Utilities | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Utilities | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 28.5 | 19.8 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Utilities | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Materials |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 22.5 | 26.3 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Materials | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Materials | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 22.5 | 26.3 |  |
Fair value measured on a recurring basis | Debt securities issued by corporations | Materials | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Mortgage-backed and asset-backed securities |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 148.8 | 133.5 |  |
Fair value measured on a recurring basis | Mortgage-backed and asset-backed securities | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Mortgage-backed and asset-backed securities | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 148.8 | 133.5 |  |
Fair value measured on a recurring basis | Mortgage-backed and asset-backed securities | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Municipal obligations |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 285.4 | 280.3 |  |
Fair value measured on a recurring basis | Municipal obligations | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Municipal obligations | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 285.4 | 280.3 |  |
Fair value measured on a recurring basis | Municipal obligations | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Fixed maturity investments |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 1,132.0 | 1,077.5 |  |
Fair value measured on a recurring basis | Fixed maturity investments | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 153.0 | 153.2 |  |
Fair value measured on a recurring basis | Fixed maturity investments | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 979.0 | 924.3 |  |
Fair value measured on a recurring basis | Fixed maturity investments | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Short-term investments |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Short-term investments, at fair value | 269.8 | 214.2 |  |
Fair value measured on a recurring basis | Short-term investments | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Short-term investments, at fair value | 249.0 | 204.4 | $ 763.0 | $ 176.1
Fair value measured on a recurring basis | Short-term investments | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Short-term investments, at fair value | 20.8 | 9.8 |  |
Fair value measured on a recurring basis | Short-term investments | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Short-term investments, at fair value | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Financials |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 13.5 |  |
Fair value measured on a recurring basis | Common equity securities | Financials | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 13.5 |  |
Fair value measured on a recurring basis | Common equity securities | Financials | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Financials | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Health Care |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 14.0 |  |
Fair value measured on a recurring basis | Common equity securities | Health Care | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 14.0 |  |
Fair value measured on a recurring basis | Common equity securities | Health Care | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Health Care | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Energy |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 4.1 |  |
Fair value measured on a recurring basis | Common equity securities | Energy | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 4.1 |  |
Fair value measured on a recurring basis | Common equity securities | Energy | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Energy | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Consumer |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 6.2 |  |
Fair value measured on a recurring basis | Common equity securities | Consumer | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 6.2 |  |
Fair value measured on a recurring basis | Common equity securities | Consumer | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Consumer | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Industrial |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 11.4 |  |
Fair value measured on a recurring basis | Common equity securities | Industrial | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 11.4 |  |
Fair value measured on a recurring basis | Common equity securities | Industrial | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Industrial | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Technology |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 7.4 |  |
Fair value measured on a recurring basis | Common equity securities | Technology | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 7.4 |  |
Fair value measured on a recurring basis | Common equity securities | Technology | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Technology | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Communications |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 12.7 |  |
Fair value measured on a recurring basis | Common equity securities | Communications | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 12.7 |  |
Fair value measured on a recurring basis | Common equity securities | Communications | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Communications | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Materials |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 3.1 |  |
Fair value measured on a recurring basis | Common equity securities | Materials | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 3.1 |  |
Fair value measured on a recurring basis | Common equity securities | Materials | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Materials | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments |  | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Exchange traded funds |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 712.3 | 675.3 |  |
Fair value measured on a recurring basis | Common equity securities | Exchange traded funds | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 646.3 | 617.0 |  |
Fair value measured on a recurring basis | Common equity securities | Exchange traded funds | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 66.0 | 58.3 |  |
Fair value measured on a recurring basis | Common equity securities | Exchange traded funds | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Other |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 192.7 | 177.9 |  |
Fair value measured on a recurring basis | Common equity securities | Other | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Other | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 192.7 | 177.9 |  |
Fair value measured on a recurring basis | Common equity securities | Other | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Common equity securities | Common equity securities |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 905.0 | 925.6 |  |
Fair value measured on a recurring basis | Common equity securities | Common equity securities | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 646.3 | 689.4 |  |
Fair value measured on a recurring basis | Common equity securities | Common equity securities | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 258.7 | 236.2 |  |
Fair value measured on a recurring basis | Common equity securities | Common equity securities | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 | 0.0 |  |
Fair value measured on a recurring basis | Other long-term investments |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 275.1 | 138.7 |  |
Fair value measured on a recurring basis | Other long-term investments | Level 1 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 |  |  |
Fair value measured on a recurring basis | Other long-term investments | Level 2 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | 0.0 |  |  |
Fair value measured on a recurring basis | Other long-term investments | Level 3 Inputs |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Fair value investments | $ 275.1 | $ 138.7 |  |

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