ORGANIZATION AND BASIS OF PRESENTATION (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2017	Jan. 01, 2017	Dec. 31, 2016
Summary of significant accounting policies
Increase in deferred revenue	$ 15,489		$ 9,802
Other current liabilities	6,651		9,414
Decrease in retained earnings	(600,253)		(626,600)
Cumulative effect of accounting changes					$ 0
Restricted cash	4,135		3,837	$ 4,100		$ 4,100
Operating lease, right-of-use, estimated asset and liability (approximate)	22,000
Accounting Standards Update 2016-01 | Accumulated other comprehensive income (loss)
Summary of significant accounting policies
Cumulative effect of accounting changes		$ 733
Accounting Standards Update 2014-09
Summary of significant accounting policies
Cumulative effect of accounting changes		10,448
Accounting Standards Update 2014-09 | Adjustments
Summary of significant accounting policies
Increase in deferred revenue	(6,655)	11,200
Increase unbilled accounts receivable		1,100
Other current liabilities	348
Decrease in retained earnings	(10,169)	$ 10,400
Lenders One
Summary of significant accounting policies
Total assets	4,800		4,600
Total liabilities	$ 3,200		$ 3,100