Long-Term Debt (Schedule of Interest Rate Swap Agreements) (Details) - Interest rate swap contracts - USD ($) $ in Millions			1 Months Ended	3 Months Ended					9 Months Ended
		Mar. 27, 2019	Nov. 30, 2019	Mar. 31, 2020		Jun. 30, 2019	Mar. 31, 2019		Dec. 31, 2019		Nov. 05, 2019	Dec. 31, 2018	[1]
Derivative [Line Items]
Balance at the beginning of the period				$ 550		$ 650	$ 650		$ 650
Terminated		$ (441)	$ (171)			$ (38)	(441)		(650)
Entered into effect									550
Balance at the end of the period		$ 650		$ 550			$ 650		$ 550
Fix Rate, Entered into effect	[1]								1.615%
Weighted Average Fixed Rate (as a percent)				1.615%	[1]		1.493%	[1]	1.615%	[1]	1.615%	1.493%

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