Employee Retirement Benefit Plans - Components of Company's Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions		3 Months Ended
		Sep. 30, 2017	Sep. 30, 2016
Components of net periodic benefit cost:
Defined Benefit Plan, Service Cost		$ 0.9	$ 0.8
Defined Benefit Plan, Interest Cost		1.8	1.7
Defined Benefit Plan, Expected Return (Loss) on Plan Assets		(2.9)	(2.8)
Defined Benefit Plan, Amortization of Gain (Loss)	[1]	0.6	1.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		0.4	$ 0.8
Estimated discounted value of future employer contributions		39.1
Estimated annual cash contribution		$ 1.7

[1] Amount represents the amortization of unrecognized actuarial gains/(losses).