PROPERTY, EQUIPMENT AND SOFTWARE, NET (Schedule of Property, Equipment and Software) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	$ 223,143	$ 210,039
Less accumulated depreciation	(115,254)	(106,388)
Property, equipment and software, net	107,889	103,651	[1]
Capitalized website and internal-use software development costs
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	87,860	81,710
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	77,892	74,236
Computer equipment
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	34,889	32,450
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	17,093	16,435
Telecommunication
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	4,197	3,996
Software
Property, Plant and Equipment [Line Items]
Property, equipment and software, gross	$ 1,212	$ 1,212

[1] As of January 1, 2018, the Company adopted Accounting Standards Update 2014-09, "Revenue from Contracts with Customers (Topic 606)" ("ASC 606"), using the full retrospective method. Accordingly, the Company has recast certain amounts in prior periods presented. See Note 1 below for additional discussion.