PROPERTY AND EQUIPMENT (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($) building	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Property and Equipment
Unamortized capitalized software development costs	$ 9,400	$ 9,500	$ 9,400
Capitalized software development amortization expense		5,700	4,300	$ 2,600
Rental Income, Nonoperating		$ 1,600
Two Office Buildings In Charlotte, NC
Property and Equipment
Number of office buildings acquired | building	2
Cash payment for asset purchase	$ 23,476		23,476
Capitalized acquisition-related costs			$ 100