Long-Term Debt (Schedule of Interest Rate Swap Agreements) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Balance at the beginning of the period		$ 650,000,000	$ 650,000,000
Terminated		650,000,000
Balance at the end of the period		$ 550,000,000	$ 650,000,000
Weighted Average Fixed Rate (as a percent)	[1]	1.615%	1.493%	1.493%
Entered into effect		$ 550,000,000
Interest Rate Swap Contracts [Member]
Derivative [Line Items]
Terminated		$ (650,000,000)

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