Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	May 31, 2024	May 31, 2023
Income Tax Disclosure [Abstract]
Compensation and employee benefit liabilities	$ 60.3	$ 52.4
Other current liabilities	12.4	17.3
Tax credit carry forward	0.2	0.2
Stock-based compensation	16.5	14.8
Unrealized losses on available-for-sale securities	40.1	43.4
Capitalization of research and development	68.6	54.1
Leases	13.9	15.9
Net operating loss ("NOL") carry forwards	5.0	5.1
Tax benefit of uncertain tax positions	16.2	13.6
Gross deferred tax assets	233.2	216.8
Deferred contract costs	151.2	151.3
Capitalized software	58.2	56.5
Depreciation	0.3	2.4
Goodwill and Intangible assets	91.8	99.1
Operating lease right-of-use assets	9.5	13.7
Other	7.7	5.7
Gross deferred tax liabilities	318.7	328.7
Net deferred tax liability	$ (85.5)	$ (111.9)