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Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Debt Securities, Available-for-sale, Amortized Cost | $ 2,739 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | $ 0
Premium Receivable, Allowance for Credit Loss | $ 13 | $ 17
Preferred stock, par value | $ 0.01 |
Preferred stock, shares authorized | 20,000,000 |
Preferred Stock, Shares Issued | 0 |
Common stock, par value | $ 0.01 |
Common stock, shares authorized | 130,000,000 |
Common stock, shares issued | 46,477,067 | 45,865,081
Common stock, shares outstanding | 46,197,102 |
Treasury stock, shares | 279,965 | 55,942
Equity investments in pooled funds [Member] |  |
Other Investment Not Readily Marketable, Fair Value | $ 600 | $ 544
Variable Interest Entity, Primary Beneficiary [Member] |  |
Long-term debt | $ 4,264 | $ 4,324

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