Fair Value of Financial Instruments - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Jun. 30, 2014
Cash and cash equivalents:
Money market funds	$ 86.8	[1]	$ 138.9	[1]
Other current assets:
Available-for-sale equity securities	0.1		0.1
Other non-current assets:
Available-for-sale equity securities	24.3		20.9
Total	111.2		159.9
Level 1 [Member]
Cash and cash equivalents:
Money market funds	86.8	[1]	138.9	[1]
Other current assets:
Available-for-sale equity securities	0.1		0.1
Other non-current assets:
Available-for-sale equity securities	23.2		19.8
Total	110.1		158.8
Level 2 [Member]
Cash and cash equivalents:
Money market funds	0	[1]	0	[1]
Other current assets:
Available-for-sale equity securities	0		0
Other non-current assets:
Available-for-sale equity securities	0		0
Total	0		0
Level 3 [Member]
Cash and cash equivalents:
Money market funds	0	[1]	0	[1]
Other current assets:
Available-for-sale equity securities	0		0
Other non-current assets:
Available-for-sale equity securities	1.1		1.1
Total	$ 1.1		$ 1.1

[1] Money market funds include MMDA account balances of $55.2 million and $71.6 million as of December 31, 2014 and June 30, 2014, respectively.