Income Taxes - Schedule Of Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 84.1	$ 43.4
Accrued expenses	12.4	1.5
Operating lease liabilities	3.5	3.3
Stock-based compensation	1.9	3.7
Warrants	6.0	2.5
Capitalized R&D expenses	77.8	51.7
Credits	41.7	21.1
Start-up costs	3.8	4.7
Other	0.7	0.9
Gross deferred tax assets	231.9	132.8
Less: valuation allowance	(226.3)	(129.7)
Deferred tax assets, net of valuation allowance	5.6	3.1
Deferred tax liabilities:
Depreciation and amortization	(3.7)	0.0
Right-of-use assets	(1.9)	(3.1)
Total deferred tax liabilities	(5.6)	(3.1)
Total net deferred tax assets	$ 0.0	$ 0.0