Income Taxes - Deferred Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carry-forwards	$ 44.4	$ 57.2
Research and other credit carry-forwards	294.4	281.3
Deferred revenue	74.9	58.1
Share-based compensation	25.4	17.2
Capitalized R&D expenditure	475.7	293.1
Reserves and accruals not currently deductible	133.0	66.1
Operating lease liabilities	31.9	39.7
Other	12.1	13.2
Total deferred tax assets	1,091.8	825.9
Valuation allowance	(326.9)	(310.9)
Deferred tax assets, net of valuation allowance	764.9	515.0
Deferred tax liabilities:
Property and equipment basis differences	(5.5)	0.0
Purchased intangible assets	(23.0)	(32.3)
Unremitted foreign earnings	(24.1)	(23.7)
Net unrealized gain	(41.9)	(35.8)
Operating lease assets	(29.5)	(36.1)
Total deferred tax liabilities	(124.0)	(127.9)
Net deferred tax assets	$ 640.9	$ 387.1