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	Sep. 30, 2013	Jun. 30, 2013
Cash and cash equivalents:
Money market funds	$ 33.4	$ 122.1
Other current assets:
Available-for-sale equity securities
Other non-current assets:
Available-for-sale equity securities	18.6	16.9
Total	52.0	139.0
Level 1 [Member]
Cash and cash equivalents:
Money market funds	33.4	122.1
Other current assets:
Available-for-sale equity securities
Other non-current assets:
Available-for-sale equity securities	17.5	15.8
Total	50.9	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