Employee Benefit Plans (Narrative) (Details)	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets in defined benefit pension plan	$ 2,665,000,000	$ 2,499,000,000
Estimated employer contributions for defined benefit plans for the next year	$ 0
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%
Percent of qualified earnings contributed by employee matched by the Corporation	4.00%
Defined contribution plan expense	$ 27,000,000	24,000,000	$ 24,000,000
Qualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated average life of pension plan in years	9
Fair value of plan assets in defined benefit pension plan	$ 2,681,000,000	2,508,000,000	3,462,000,000
Non-Qualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets in defined benefit pension plan	0	0	0
Postretirement Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets in defined benefit pension plan	$ 45,000,000	$ 46,000,000	$ 53,000,000
Minimum | Qualified Plan | Debt securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	35.00%
Maximum | Qualified Plan | Debt securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	45.00%