FIXED ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation of fixed assets	$ 26,411	$ 28,848	$ 27,283
Fixed assets, gross	339,589	315,778
Less: accumulated depreciation	(204,902)	(186,435)
Total fixed assets, net	134,687	129,343
Write-off of fully depreciated assets	8,000
Computer hardware and software, including internal-use software and website development
Property, Plant and Equipment [Line Items]
Fixed assets, gross	215,412	196,501
Building
Property, Plant and Equipment [Line Items]
Fixed assets, gross	69,266	69,169
Furniture and equipment
Property, Plant and Equipment [Line Items]
Fixed assets, gross	17,066	14,455
Land
Property, Plant and Equipment [Line Items]
Fixed assets, gross	12,781	12,781
Building machinery and equipment
Property, Plant and Equipment [Line Items]
Fixed assets, gross	9,713	8,356
Leasehold improvements
Property, Plant and Equipment [Line Items]
Fixed assets, gross	8,379	7,752
Land improvements
Property, Plant and Equipment [Line Items]
Fixed assets, gross	6,972	6,764
Equipment under capital leases
Property, Plant and Equipment [Line Items]
Depreciation of fixed assets	500	3,500	$ 4,100
Fixed assets, gross	1,800	1,800
Less: accumulated depreciation	$ (1,000)	$ (500)