Employee Benefit Plans - Other Post-retirement Benefit Plan (Details) - Executive Retiree Health Insurance Plan - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, maximum age eligibility	65 years
Benefit expense	$ 0.5	$ 0.5	$ 0.4
Benefit obligation	$ 4.5	$ 5.2	$ 5.3