Income Taxes (Operating Loss Carryforwards Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Valuation Allowance	$ 504
Operating Loss Carryforwards, Additional Valuation Allowance	1
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss and credit carryforwards	825
Operating loss carryforwards expected to be utilized	202
State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss and credit carryforwards	7,600
Operating loss carryforwards expected to be utilized	$ 541
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2019
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2038