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Condensed Financial Information (Parent Company Only) - Condensed Balance Sheets (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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Condensed balance sheets: |  |
Cash and cash equivalents | $ 2,276.8 | $ 1,076.8
Investment in subsidiaries, at equity: |  |
Other assets | 215.3 | 187.6
Total assets | 17,648.7 | 14,644.2
Long-term debt | 98.6 | 0.0
Subordinated debentures held by subsidiary trusts | 87.0 | 86.9
Total liabilities | 15,688.9 | 12,630.3
Stockholders’ equity | 1,959.8 | 2,013.9
Total liabilities and stockholders’ equity | 17,648.7 | 14,644.2
Parent Company |  |
Condensed balance sheets: |  |
Cash and cash equivalents | 123.2 | 147.1
Investment in subsidiaries, at equity: |  |
Equity method investments | 1,986.6 | 1,899.3
Advances from subsidiaries, net | 41.0 | 48.9
Other assets | 61.3 | 61.7
Total assets | 2,212.1 | 2,157.0
Other liabilities | 66.7 | 56.2
Subordinated debentures held by subsidiary trusts | 87.0 | 86.9
Total liabilities | 252.3 | 143.1
Stockholders’ equity | 1,959.8 | 2,013.9
Total liabilities and stockholders’ equity | $ 2,212.1 | $ 2,157.0

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