SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue
Total revenues	$ 87,074	$ 90,385	$ 91,566	$ 85,180	$ 78,649	$ 87,028	$ 92,498	$ 86,725	$ 354,205	$ 344,900	$ 336,508
IGS
Disaggregation of Revenue
Total revenues									214,406	203,247	192,200
DHR
Disaggregation of Revenue
Total revenues									91,059	100,241	103,899
Other
Disaggregation of Revenue
Total revenues									29,575	22,634	23,527
Total transaction-based
Disaggregation of Revenue
Total revenues									335,040	326,122	319,626
Development services
Disaggregation of Revenue
Total revenues									10,285	12,146	10,180
Fixed-fee services
Disaggregation of Revenue
Total revenues									8,880	6,632	6,702
State Enterprise
Disaggregation of Revenue
Total revenues									320,700	320,584	311,351
State Enterprise | IGS
Disaggregation of Revenue
Total revenues									214,406	203,247	192,200
State Enterprise | DHR
Disaggregation of Revenue
Total revenues									91,059	100,241	103,899
State Enterprise | Other
Disaggregation of Revenue
Total revenues									0	0	0
State Enterprise | Total transaction-based
Disaggregation of Revenue
Total revenues									305,465	303,488	296,099
State Enterprise | Development services
Disaggregation of Revenue
Total revenues									10,285	12,146	10,180
State Enterprise | Fixed-fee services
Disaggregation of Revenue
Total revenues									4,950	4,950	5,072
Software & Services
Disaggregation of Revenue
Total revenues									33,505	24,316	25,157
Software & Services | IGS
Disaggregation of Revenue
Total revenues									0	0	0
Software & Services | DHR
Disaggregation of Revenue
Total revenues									0	0	0
Software & Services | Other
Disaggregation of Revenue
Total revenues									29,575	22,634	23,527
Software & Services | Total transaction-based
Disaggregation of Revenue
Total revenues									29,575	22,634	23,527
Software & Services | Development services
Disaggregation of Revenue
Total revenues									0	0	0
Software & Services | Fixed-fee services
Disaggregation of Revenue
Total revenues									$ 3,930	$ 1,682	$ 1,630