Income Taxes (Schedule Of Statutory Federal Income Tax Rate Reconciles To Actual Income Tax Expense (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Deferred Tax Assets, Valuation Allowance	$ 0	$ 2
Income tax expense (benefit) at statutory federal rate	240	327	$ 247
State income taxes, net	40	21	15
Other nondeductible expenses	15	3	3
Nontaxable income	(24)	(33)	(25)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount	(7)	(8)	0
Tax credits and other taxes	0	(1)	(2)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	(2)	47	0
Other	(3)	(14)	(2)
Income Tax Expense (Benefit), Total	$ 259	$ 344	$ 236