Income Taxes (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Current income tax expense (benefit):
Federal	$ 63	$ 0	$ 0
State	26	13	(11)
Total current	89	13	(11)
Deferred income tax expense (benefit):
Federal	181	266	399
State	64	73	51
Total deferred	245	339	450
Non-current tax expense (benefit)	30	14	11
Income tax expense (benefit)	$ 364	$ 366	$ 450
Federal statutory tax rate			0.21
Additional tax expense related to the federal tax reform law			$ 58