PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	$ 106,406		$ 106,406		$ 95,142
Less: accumulated depreciation and amortization	(52,589)		(52,589)		(44,180)
Property, equipment and capitalized software, net	53,817		53,817		50,962
Depreciation expense
Depreciation expense	4,551	$ 3,681	8,924	$ 7,003
Amortization of capital leases	26	$ 46	53	$ 68
Office and computer equipment
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	24,740		24,740		23,844
Leasehold improvements
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	12,028		12,028		11,999
Purchased software
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	10,924		10,924		9,916
Capitalized software
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	46,517		46,517		39,432
Furniture and fixtures
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	4,984		4,984		4,894
Land
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	390		390		390
Building
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	1,797		1,797		1,750
Work in process
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	5,026		5,026		2,917
Assets held under capital leases
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Property, equipment and capitalized software, net	660		660		961
Capitalized software and work in process
PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE
Total	$ 32,992		$ 32,992		$ 28,417