SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 87,028	$ 84,533	$ 266,251	$ 253,036
IGS
Disaggregation of Revenue [Line Items]
Revenues	51,085	48,089	156,463	144,194
DHR
Disaggregation of Revenue [Line Items]
Revenues	25,555	25,936	79,439	79,787
Other
Disaggregation of Revenue [Line Items]
Revenues	6,144	8,099	18,021	20,073
Total transaction-based
Disaggregation of Revenue [Line Items]
Revenues	82,784	82,124	253,923	244,054
Portal software development & services
Disaggregation of Revenue [Line Items]
Revenues	3,006	1,134	8,615	5,157
Portal management
Disaggregation of Revenue [Line Items]
Revenues	1,238	1,275	3,713	3,825
Outsourced Portals
Disaggregation of Revenue [Line Items]
Revenues	80,884	76,434	248,230	232,963
Outsourced Portals | IGS
Disaggregation of Revenue [Line Items]
Revenues	51,085	48,089	156,463	144,194
Outsourced Portals | DHR
Disaggregation of Revenue [Line Items]
Revenues	25,555	25,936	79,439	79,787
Outsourced Portals | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Outsourced Portals | Total transaction-based
Disaggregation of Revenue [Line Items]
Revenues	76,640	74,025	235,902	223,981
Outsourced Portals | Portal software development & services
Disaggregation of Revenue [Line Items]
Revenues	3,006	1,134	8,615	5,157
Outsourced Portals | Portal management
Disaggregation of Revenue [Line Items]
Revenues	1,238	1,275	3,713	3,825
Other Software & Services
Disaggregation of Revenue [Line Items]
Revenues	6,144	8,099	18,021	20,073
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	6,144	8,099	18,021	20,073
Other Software & Services | Total transaction-based
Disaggregation of Revenue [Line Items]
Revenues	6,144	8,099	18,021	20,073
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