SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 92,498	$ 85,326	$ 179,223	$ 168,503
IGS
Disaggregation of Revenue [Line Items]
Revenues	55,111	50,217	105,379	96,142
DHR
Disaggregation of Revenue [Line Items]
Revenues	26,645	25,689	53,883	53,858
Other
Disaggregation of Revenue [Line Items]
Revenues	5,943	5,952	11,877	11,931
Total transaction-based
Disaggregation of Revenue [Line Items]
Revenues	87,699	81,858	171,139	161,931
Portal software development & services
Disaggregation of Revenue [Line Items]
Revenues	3,562	2,193	5,609	4,022
Portal management
Disaggregation of Revenue [Line Items]
Revenues	1,237	1,275	2,475	2,550
Outsourced Portals
Disaggregation of Revenue [Line Items]
Revenues	86,555	79,374	167,346	156,572
Outsourced Portals | IGS
Disaggregation of Revenue [Line Items]
Revenues	55,111	50,217	105,379	96,142
Outsourced Portals | DHR
Disaggregation of Revenue [Line Items]
Revenues	26,645	25,689	53,883	53,858
Outsourced Portals | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Outsourced Portals | Total transaction-based
Disaggregation of Revenue [Line Items]
Revenues	81,756	75,906	159,262	150,000
Outsourced Portals | Portal software development & services
Disaggregation of Revenue [Line Items]
Revenues	3,562	2,193	5,609	4,022
Outsourced Portals | Portal management
Disaggregation of Revenue [Line Items]
Revenues	1,237	1,275	2,475	2,550
Other Software & Services
Disaggregation of Revenue [Line Items]
Revenues	5,943	5,952	11,877	11,931
Other Software & Services | IGS
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other Software & Services | DHR
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other Software & Services | Other
Disaggregation of Revenue [Line Items]
Revenues	5,943	5,952	11,877	11,931
Other Software & Services | Total transaction-based
Disaggregation of Revenue [Line Items]
Revenues	5,943	5,952	11,877	11,931
Other Software & Services | Portal software development & services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other Software & Services | Portal management
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0	$ 0	$ 0