Income Taxes - Components of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2026	Jun. 30, 2025
Deferred tax assets:
Accrued expenses not currently deductible	$ 294.9	$ 256.7
Stock-based compensation expense	59.8	56.0
Foreign tax credits	9.6	8.8
Fixed and intangible assets	80.7	216.8
Net operating losses	57.4	59.3
Disallowed business interest expense carryforward	0.0	30.9
Unrealized investment losses, net	106.1	98.4
Other	32.2	28.5
Deferred tax assets, gross	640.7	755.4
Less: valuation allowances	(24.1)	(23.8)
Deferred tax assets, net	616.6	731.6
Deferred tax liabilities:
Deferred contract costs	664.9	654.0
Prepaid expenses	122.3	103.1
Prepaid retirement benefits	76.6	53.1
Tax on unrepatriated earnings	10.4	12.0
Other	17.3	16.9
Deferred tax liabilities	891.5	839.1
Net deferred tax (liabilities)/assets	$ (274.9)	$ (107.5)