Income Taxes (Reconciliation Of Provision (Benefit) For Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Abstract]
Expected provision (benefit) at federal statutory rate	$ (2,296)	$ 507	$ 417
Increase (decrease) resulting from:
State income taxes, net of federal income tax effect	(194)	58	53
Nondeductible expenses		3	3
State rate redetermination		(48)	4
Change in valuation allowance	488	5
Other	(3)		9
Provision (Benefit) for Income Taxes	$ (2,005)	$ 525	$ 486