SEGMENT INFORMATION - Schedule of Changes in Carrying Amount of Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 320.8
Foreign currency translation adjustment	(3.7)
Balance at end of period	317.1
Office Segment
Goodwill [Roll Forward]
Balance at beginning of period	39.1
Foreign currency translation adjustment	0.1
Balance at end of period	39.2
Studio Segment
Goodwill [Roll Forward]
Balance at beginning of period	281.7
Foreign currency translation adjustment	(3.8)
Balance at end of period	$ 277.9