SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 939.2	$ 372.4
Restricted cash included in Prepaid expenses and other current assets	25.0	0.0
Cash, cash equivalents, and restricted cash	$ 964.2	$ 372.4	$ 482.7	$ 341.3