Income Taxes (Schedule of Provision for Income Taxes for Income from Continuing Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal		$ 5	$ 7
State	$ 5	7	7
Total, Current	5	12	14
Deferred:
Federal	(485)	(88)	103
State	31	(28)	(1)
Total, Deferred	(454)	(116)	102
Total (benefit from) provision for income taxes for (loss) income from continuing operations	$ (449)	$ (104)	$ 116