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, 2013	Jun. 30, 2013
Cash and cash equivalents:
Money market funds	$ 76.0	$ 122.1
Other current assets:
Available-for-sale equity securities
Other non-current assets:
Available-for-sale equity securities	19.9	16.9
Total	95.9	139.0
Level 1 [Member]
Cash and cash equivalents:
Money market funds	76.0	122.1
Other current assets:
Available-for-sale equity securities
Other non-current assets:
Available-for-sale equity securities	18.8	15.8
Total	94.8	137.9
Level 2 [Member]
Cash and cash equivalents:
Money market funds
Other current assets:
Available-for-sale equity securities
Other non-current assets:
Available-for-sale equity securities
Total
Level 3 [Member]
Cash and cash equivalents:
Money market funds
Other current assets:
Available-for-sale equity securities
Other non-current assets:
Available-for-sale equity securities	1.1	1.1
Total	$ 1.1	$ 1.1