Long-Term Debt And Lease Obligation Long-term Debt and Lease Obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Long-term Debt and Lease Obligation [Abstract]
Finance Lease, Right-of-Use Asset, Amortization	$ 15	$ 9
Operating Lease, Expense	4	4
Total Finance and Operating Lease Cost	19	13
Finance Lease, Principal Payments	$ 15	$ 15
Finance Lease, Weighted Average Discount Rate, Percent	2.62%	2.96%
Finance Lease, Weighted Average Remaining Lease Term	3 years 8 months 1 day	3 years 7 months 24 days
Operating Lease, Payments	$ 8	$ 8
Operating Lease, Weighted Average Discount Rate, Percent	3.65%	3.69%
Operating Lease, Weighted Average Remaining Lease Term	4 years 10 months 2 days	4 years 8 months 15 days