Organization and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Total costs and expenses	$ 185.0	$ 176.5	$ 189.6	$ 102.8	$ 180.7	$ 189.2	$ 179.5	$ 171.8	$ 653.9	$ 721.2	$ 587.1	$ 588.9
Operating income (loss)	15.9	14.6	3.1	85.1	18.9	5.5	17.2	7.1	118.7	48.7	153.4	133.6
Total other expense	$ 0.2	$ (0.5)	$ (0.7)	$ (0.8)	$ (1.0)	$ 0.3	$ (4.9)	$ (2.2)	$ (1.8)	(7.8)	$ 2.6	$ 0.7
Equipment [Member] | Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Estimated useful lives, in years									5 years
Equipment [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Estimated useful lives, in years									7 years
Leasehold Improvements [Member] | Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Estimated useful lives, in years									3 years
Leasehold Improvements [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Estimated useful lives, in years									10 years
Overstated [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Total costs and expenses										0.8
Understated [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Operating income (loss)										0.8
Total other expense										$ 0.8