FURNITURE, FIXTURES AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Furniture, fixtures and equipment
Accumulated depreciation	$ (10,705)	$ (8,645)
Furniture, fixtures and equipment, net	5,229	4,789	$ 3,021
Depreciation expense	3,207	1,903	$ 1,760
Computer hardware, software and other office equipment
Furniture, fixtures and equipment
Furniture, fixture and equipment, gross	$ 6,250	5,317
Computer hardware, software and other office equipment | Minimum
Furniture, fixtures and equipment
Estimated Useful Lives	2 years
Computer hardware, software and other office equipment | Maximum
Furniture, fixtures and equipment
Estimated Useful Lives	5 years
Furniture, fixtures and leasehold improvements
Furniture, fixtures and equipment
Furniture, fixture and equipment, gross	$ 2,715	2,441
Furniture, fixtures and leasehold improvements | Minimum
Furniture, fixtures and equipment
Estimated Useful Lives	2 years
Furniture, fixtures and leasehold improvements | Maximum
Furniture, fixtures and equipment
Estimated Useful Lives	5 years
Internal-use software and development costs
Furniture, fixtures and equipment
Furniture, fixture and equipment, gross	$ 6,969	$ 5,676
Internal-use software and development costs | Minimum
Furniture, fixtures and equipment
Estimated Useful Lives	3 years
Internal-use software and development costs | Maximum
Furniture, fixtures and equipment
Estimated Useful Lives	5 years