Stock-Based Compensation - Components Of Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Pre-tax stock-based compensation expense	$ 8.6	$ 3.2	$ 11.5	$ 6.2
Income tax benefit	2.4	0.5	2.9	1.3
Cost of revenues
Defined Benefit Plan Disclosure [Line Items]
Pre-tax stock-based compensation expense	0.6	0.3	0.9	0.6
Selling, general and administrative expenses
Defined Benefit Plan Disclosure [Line Items]
Pre-tax stock-based compensation expense	$ 8.0	$ 2.9	$ 10.6	$ 5.6