Income Taxes (Net Operating Loss Carryforwards) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Federal
Operating Loss Carryforwards	$ 521	$ 640
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2032
State
Operating Loss Carryforwards	$ 1,577	$ 1,776
Operating Loss Carryforwards Earliest Expiration Date	2019
Operating Loss Carryforwards Latest Expiration Date	2036