Employee Retirement Benefit Plans - Components of Company's Net Periodic Benefit Costs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2015	Mar. 31, 2014	Jun. 30, 2014
Components of net periodic benefit cost:
Service cost	$ 0.6		$ 0.7		$ 2.1	$ 2.1
Interest cost	2.8		3.1		8.8	9.2
Expected return on plan assets	(2.6)		(2.7)		(8.0)	(7.8)
Amortization	0.3	[1]	0.3	[1]	1.2	0.9
Net amount recognized	1.1		1.4		4.1	4.4
Estimated discounted value of future employer contributions	39.5				39.5		39.6
Estimated annual cash contribution	$ 1.7				$ 1.7

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