Employee Retirement Benefits (Fair Value Hierarchy Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	$ 357	$ 354	$ 318
Fixed Maturities
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	60	77
Fixed Maturities | Level 1
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	31	25
Fixed Maturities | Level 2
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	29	52
Fixed Maturities | Level 3
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Fixed Maturities | States, Municipalities and Political Subdivisions
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	9	25
Fixed Maturities | States, Municipalities and Political Subdivisions | Level 1
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Fixed Maturities | States, Municipalities and Political Subdivisions | Level 2
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	9	25
Fixed Maturities | States, Municipalities and Political Subdivisions | Level 3
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Fixed Maturities | Domestic Corporate Debt Securities
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	20	27
Fixed Maturities | Domestic Corporate Debt Securities | Level 1
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Fixed Maturities | Domestic Corporate Debt Securities | Level 2
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	20	27
Fixed Maturities | Domestic Corporate Debt Securities | Level 3
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Fixed Maturities | United States Government
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	31	25
Fixed Maturities | United States Government | Level 1
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	31	25
Fixed Maturities | United States Government | Level 2
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Fixed Maturities | United States Government | Level 3
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Equity Securities
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	266	260
Equity Securities | Level 1
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	266	260
Equity Securities | Level 2
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Equity Securities | Level 3
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	0	0
Fixed Maturities And Equity Securities
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	326	337
Fixed Maturities And Equity Securities | Level 1
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	297	285
Fixed Maturities And Equity Securities | Level 2
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	29	52
Fixed Maturities And Equity Securities | Level 3
Defined Benefit Plan Fair Value Disclosure
Pension plan assets at fair value	$ 0	$ 0