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Condensed Financial Information (Parent Company Only) - Condensed Balance Sheets (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2016
--- | --- | --- | ---
Condensed balance sheets: |  |  |
Cash and cash equivalents | $ 1,076.8 | $ 822.0 |
Investment in subsidiaries, at equity: |  |  |
Other assets | 187.6 | 159.1 |
Total assets | 14,644.2 | 13,300.2 |
Subordinated debentures held by subsidiary trusts | 86.9 | 86.9 |
Total liabilities | 12,630.3 | 11,606.3 |
Stockholders’ equity | 2,013.9 | 1,693.9 | $ 982.6
Total liabilities and stockholders’ equity | 14,644.2 | 13,300.2 |
Parent Company |  |  |
Condensed balance sheets: |  |  |
Cash and cash equivalents | 147.1 | 72.9 |
Investment in subsidiaries, at equity: |  |  |
Equity method investments | 1,899.3 | 1,648.9 |
Advances from subsidiaries, net | 48.9 | 46.0 |
Other assets | 61.7 | 59.0 |
Total assets | 2,157.0 | 1,826.8 |
Other liabilities | 56.2 | 46.0 |
Subordinated debentures held by subsidiary trusts | 86.9 | 86.9 |
Total liabilities | 143.1 | 132.9 |
Stockholders’ equity | 2,013.9 | 1,693.9 |
Total liabilities and stockholders’ equity | $ 2,157.0 | $ 1,826.8 |

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