Income Taxes - Effective Income Tax Expense (Benefit) Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense (benefit) at the federal statutory rate of 21%	$ (177)	$ 655	$ 767
State income taxes (net of federal income tax benefit)	(5)	76	45
Deferred remeasurement due to state rate changes	47	(20)	30
Change in valuation allowance due to acquisitions	14	0	19
Change in valuation allowance excluding impact of acquisitions	(18)	(33)	(2,147)
Research and development tax credits	(31)	(3)	(19)
Transaction costs	22	0	2
Compensation costs related to acquired company	11	0	0
Other	10	23	18
Total	$ (127)	$ 698	$ (1,285)
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income tax expense (benefit) at the federal statutory rate of 21%	21.00%	21.00%	21.00%
State income taxes (net of federal income tax benefit)	0.60%	2.50%	1.20%
Deferred remeasurement due to state rate changes	(5.60%)	(0.60%)	0.80%
Change in valuation allowance due to acquisitions	(1.70%)	0.00%	0.50%
Change in valuation allowance excluding impact of acquisitions	2.10%	(1.10%)	(58.80%)
Research and development tax credits	3.70%	(0.10%)	(0.50%)
Transaction costs	(2.60%)	0.00%	0.10%
Compensation costs related to acquired company	(1.20%)	0.00%	0.00%
Other	(1.20%)	0.70%	0.50%
Total	15.10%	22.40%	(35.20%)