Debt And Related Expenses (Schedule of Net Financing Cost Components) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Debt Disclosure [Abstract]
Interest based on debt outstanding	$ 81	$ 98	$ 177	$ 195
Early retirement of debt			312
Capitalized interest	(17)	(16)	(35)	(32)
Other	(2)	(5)	(5)	(3)
Total net financing costs	$ 62	$ 77	$ 449	$ 160