ACQUISITIONS - CastleLine (Details) - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
	Jul. 17, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2016
Acquisitions
Value of common stock paid at acquisition		$ 0	$ 21,733	$ 0
Goodwill		$ 86,283	$ 82,801	$ 90,851
CastleLine
Acquisitions
Cash paid at acquisition	$ 12,300
Accounts payable	$ 10,500
Contingent consideration arrangements, payment period	4 years
Number of shares exchanged for acquisition	495
Value of common stock paid at acquisition	$ 14,400
Additional consideration	3,800
Cash					$ 1,088
Accounts receivable, net					100
Prepaid expenses					20
Restricted cash					2,501
Non-compete agreements					1,130
Databases/other					1,800
Customer relationships					395
Trademarks and trade names					160
Deferred taxes					356
Goodwill					26,730
Assets acquired					34,280
Accounts payable and accrued expenses					(837)
Deferred revenue					0
Purchase price					33,443
CastleLine | Initial purchase price allocation
Acquisitions
Business combination, consideration transferred	33,400
Cash	1,088
Accounts receivable, net	510
Prepaid expenses	66
Restricted cash	2,501
Non-compete agreements	1,105
Databases/other	465
Customer relationships	395
Trademarks and trade names	150
Deferred taxes	0
Goodwill	28,125
Assets acquired	34,405
Accounts payable and accrued expenses	(875)
Deferred revenue	(87)
Purchase price	$ 33,443
CastleLine | Adjustments
Acquisitions
Cash					0
Accounts receivable, net					(410)
Prepaid expenses					(46)
Restricted cash					0
Non-compete agreements					25
Databases/other					1,335
Customer relationships					0
Trademarks and trade names					10
Deferred taxes					356
Goodwill					(1,395)
Assets acquired					(125)
Accounts payable and accrued expenses					38
Deferred revenue					87
Purchase price					$ 0