Employee Benefit Plans (Schedule of Estimated Future Employer Contributions) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Qualified Plan
2019	$ 134
2020	133
2021	136
2022	137
2023	139
2024 - 2028	683
Non-Qualified Plan
2019	14
2020	14
2021	14
2022	15
2023	15
2024 - 2028	74
Postretirement Benefit Plan
2019	5	[1]
2020	5	[1]
2021	5	[1]
2022	5	[1]
2023	4	[1]
2024 - 2028	$ 16	[1]

[1] Estimated benefit payments in the postretirement benefit plan are net of estimated Medicare subsidies.