Prepaid Expenses and Other Assets - Additional Information (Detail) - Partnership Agreement [Member] - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2015	Mar. 31, 2019	Mar. 31, 2018	Jun. 30, 2018
Prepaid expenses and other assets [Line Items]
Partnership agreement			10 years
Upfront cash payment			$ 10.0
Prepaid expenses and other assets	$ 1.0			$ 1.0		$ 1.0
Other assets, noncurrent	5.5			5.5		$ 6.3
Amortization expense	$ 0.2	$ 0.2		$ 0.8	$ 0.8