Income Taxes (Textuals) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Intraperiod income tax [Line Items]
Number of States for NOL Carryforwards	25
Federal statutory tax expense (benefit) rate	21.00%	21.00%	35.00%
Income Tax Disclosure (Textuals) [Abstract]
Unrecognized Tax Benefits	$ 29	$ 28	$ 38	$ 59
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	17
Unrecognized Tax Benefits Resulting in Net Operating Loss Carryforward	12
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	3	2
Valuation allowance	873	1,000
Valuation Allowance, Deferred Tax Asset, Change in Amount	127
Deferred Tax Assets, Net of Valuation Allowance	1,011	869
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1	(2)	$ (8)
Expiration date 2024 through 2037 [Member]
Intraperiod income tax [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	7,100
Expiration date 2020 through 2039 [Member]
Income Tax Disclosure (Textuals) [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	$ 3,200
Change in Valuation due to Merger [Member]
Income Tax Disclosure (Textuals) [Abstract]
Valuation Allowance, Deferred Tax Asset, Change in Amount		$ (58)