Statement of Financial Position (Parentheticals) $ in Millions	Jun. 30, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares
Statement of Financial Position [Abstract]
Available for sale, at amortized cost	$ 88,265	$ 85,188
Debt Securities, Available-for-sale, Allowance for Credit Loss	11	20
Held to maturity, Fair Value	11,343	12,510
Debt Securities, Held-to-maturity, Allowance for Credit Loss	37	44
short-term investments amortized cost	4,471	4,349
Premium Receivable, Allowance for Credit Loss	42	44
Reinsurance Recoverable, Allowance for Credit Loss	$ 322	$ 314
Common Shares, shares issued | shares	477,605,264	477,605,264
Common Shares, shares outstanding | shares	438,717,213	450,732,625
Common Shares in treasury, shares | shares	38,888,051	26,872,639