ACQUISITIONS AND DISPOSALS (Narrative) (Details) - USD ($)					12 Months Ended
	Oct. 10, 2017	Apr. 03, 2017	Feb. 28, 2017	Feb. 09, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 14, 2017
Business Acquisition [Line Items]
Held in escrow account					$ 28,750,000	$ 0
Net revenue					846,813,000	713,069,000	$ 549,711,000
Net income (loss)					152,858,000	(4,670,000)	(32,900,000)
Gain on disposal of a business unit					164,779,000	0	0
Goodwill related to disposed asset group					110,768,000
Nowait, Inc
Business Acquisition [Line Items]
Equity interest in acquiree, percentage			20.00%
Total purchase price			$ 39,837,000
Held in escrow account			$ 7,945,000
Escrow deposit, duration			2 years
Acquisition-related transaction costs					100,000
Net revenue					3,900,000
Cash consideration			$ 31,892,000
Turnstyle Analytics Inc
Business Acquisition [Line Items]
Total purchase price		$ 19,741,000
Held in escrow account		$ 3,093,000
Escrow deposit, duration		18 months
Acquisition-related transaction costs					300,000
Net revenue					1,300,000
Purchase consideration including acquisition compensation cost		$ 20,600,000
Compensation costs		1,000,000
Net income (loss)					(8,800,000)
Cash consideration		$ 16,648,000
Eat 24
Business Acquisition [Line Items]
Total purchase price				$ 134,158,000
Held in escrow account					1,900,000
Acquisition-related transaction costs					0	$ 200,000
Cash consideration				$ 75,000,000
Shares issued or issuable for business acquisition (in shares)				1,402,844
Fair value of common stock				$ 59,200,000
Revenues							$ 39,200,000
Escrow account | Eat 24
Business Acquisition [Line Items]
Held in escrow account				16,500,000
Cash consideration				$ 16,500,000
Shares issued or issuable for business acquisition (in shares)				308,626
Fair value of common stock				$ 13,015,000
Eat 24
Business Acquisition [Line Items]
Escrow deposit, duration	18 months
Gain on disposal of a business unit					(164,800,000)
Disposal related costs					300,000
Goodwill related to disposed asset group					$ 110,800,000
Eat 24 | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Held in escrow account	$ 28,800,000
Escrow deposit, duration	18 months
Disposal Group, Including Discontinued Operation, Additional Consideration Received								$ 1,000,000
Disposal group, cash consideration received	$ 251,700,000