DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014	[2]
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 87.1	$ 186.4	[1]	$ 326.9
Restricted cash	0.3	0.4		0.0
Total cash, cash equivalents and restricted cash	$ 87.4	$ 186.8	[2]	$ 326.9	[2]	$ 275.3

[1] Adjusted as a result of the adoption of certain accounting pronouncements as of December 31, 2017. See Note 1, "Description of Business and Summaryof Significant Accounting Policies - Recently Adopted Accounting Pronouncements," for details of these adjustments.

[2] Adjusted as a result of the adoption of certain accounting pronouncements beginning on January 1, 2017. See Note 1, "Description of Business and Summaryof Significant Accounting Policies - Recently Adopted Accounting Pronouncements," for details of these adjustments.