Statement of Financial Position (Parentheticals) $ in Millions	Sep. 30, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares
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