ACQUISITION - Summary of Preliminary Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	$ 326,356		$ 326,356	$ 142,113
Muuto Acquisition
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Cash	7,506	$ 7,506	7,506
Customer receivables	8,717	8,717	8,717
Inventory	10,824	14,675	10,824
Other current assets	447	447	447
Property, plant, and equipment, net	1,250	1,250	1,250
Intangible assets	131,325	131,300	131,325
Other non-current assets	292	292	292
Total assets acquired	160,361	164,187	160,361
Accounts payable	3,374	3,374	3,374
Other current liabilities	8,630	12,244	8,630
Deferred income taxes	28,928	29,744	28,928
Other noncurrent liabilities	1,637	1,637	1,637
Total liabilities assumed	42,569	46,999	42,569
Net assets acquired	117,792	117,188	117,792
Purchase price		311,254	311,254
Goodwill	193,462	$ 194,066	$ 193,462
Measurement period adjustments
Inventory	3,851
Intangible assets	25
Total assets acquired	(3,826)
Other current liabilities	(3,614)
Deferred income taxes	816
Total liabilities assumed	(4,430)
Net assets acquired	$ 604