Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Net operating loss carryforwards and credits
Federal	$ 2,860	$ 848
Foreign	5	7
State	249	189
Federal and state tax credits	64	28
Disallowed business interest expense carryforward	154	19
Deferred gain	46	46
Other	97	50
Less: valuation allowance	(196)	(686)
Total deferred tax assets	3,279	501
Deferred tax liabilities
Investment in limited partnership	(554)	(375)
Convertible debt	(51)	(59)
Property, plant and equipment	(2,110)	(48)
Other	(35)	(11)
Total deferred tax liabilities	(2,750)	(493)
Net deferred tax assets	$ 529	$ 8