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Statement of Financial Position (Parentheticals) $ in Millions | Sep. 30, 2021 USD ($) shares | Dec. 31, 2020 USD ($) shares
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Statement of Financial Position [Abstract] |  |
Available for sale, at amortized cost | $ 89,335 | $ 85,188
Debt Securities, Available-for-sale, Allowance for Credit Loss | 12 | 20
Held to maturity, Fair Value | 11,119 | 12,510
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 35 | 44
short-term investments amortized cost | 3,529 | 4,349
Premium Receivable, Allowance for Credit Loss | 42 | 44
Reinsurance Recoverable, Allowance for Credit Loss | $ 325 | $ 314
Common Shares in treasury, shares | shares | 43,144,862 | 26,872,639
Common Shares, shares issued | shares | 474,021,114 | 477,605,264
Common Shares, shares outstanding | shares | 430,876,252 | 450,732,625

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