Investments (Exposure To Concentrations Of Credit Risk) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	$ 55,873	$ 49,548
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	60,749	56,735
JAPAN
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	3,080	1,493
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	3,063	1,491
Canadian Province Of Ontario Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	1,377	1,303
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	2,347	2,474
Canadian Province Of Quebec Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	1,092	1,054
Available-for-sale at fair value (amortized cost of $55,873 and $49,548; allowance for credit losses of $31 and $20)	$ 1,451	$ 1,528