Long-Term Debt (Interest Rate Swap Narrative) (Details) - Interest Rate Swap Contract [Member] - USD ($) $ in Millions		1 Months Ended	6 Months Ended		9 Months Ended				12 Months Ended
	Nov. 05, 2019	Nov. 30, 2019	Dec. 31, 2019		Sep. 30, 2020		Sep. 30, 2019		Dec. 31, 2019		Dec. 31, 2018
Derivative [Line Items]
Derivative, Term of Contract	7 years
Derivative, Notional Amount	$ 550		$ 550		$ 546		$ 171		$ 550		$ 650
Derivative, Average Fixed Interest Rate	1.615%		1.615%	[1]	1.615%	[1]	1.493%	[1]	1.615%	[1]	1.493%	[1]
Derivative, Floor Interest Rate	0.00%
Derivative terminated		$ 171	$ 171		$ 4		$ 479
Amount received from terminated interest rate swap		$ 0					$ 12		$ 12
Derivative, Fixed Interest Rate	3.365%

[1] Before the application of the applicable borrowing margin.