Retirement Plans (Fair Value, Derivatives, Entities That Calculate Net Asset Value Per Share) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivatives
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 71	$ 25
Derivatives | Collateralized Securities
Defined Benefit Plan Disclosure [Line Items]
Derivative Asset	7	9
Derivative Holdings Gross Liabilities	7	0
Derivative Holdings, Net	0	9
Derivatives | Credit Default Swap
Defined Benefit Plan Disclosure [Line Items]
Derivative Asset	2	1
Derivative Holdings Gross Liabilities	0	0
Derivative Holdings, Net	2	1
Derivatives | Interest Rate Swap
Defined Benefit Plan Disclosure [Line Items]
Derivative Asset	4	16
Derivative Holdings Gross Liabilities	0	0
Derivative Holdings, Net	4	16
Derivatives | Equity Swap
Defined Benefit Plan Disclosure [Line Items]
Derivative Asset	65	3
Derivative Holdings Gross Liabilities	0	0
Derivative Holdings, Net	65	3
Derivatives | Option on Securities
Defined Benefit Plan Disclosure [Line Items]
Derivative Asset		6
Derivative Holdings Gross Liabilities		(10)
Derivative Holdings, Net		(4)
Derivatives | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	71	25
Derivative Financial Instruments, Liabilities
Defined Benefit Plan Disclosure [Line Items]
Derivative Holdings Gross Liabilities	(7)	(10)
Derivative Financial Instruments, Assets
Defined Benefit Plan Disclosure [Line Items]
Derivative Asset	$ 78	$ 35