REPORTABLE SEGMENT AND RELATED INFORMATION - Summary of Financial Information for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 134,590	$ 90,385	$ 319,298	$ 267,132
Costs & expenses	101,256	68,890	245,306	207,381
Depreciation & amortization	3,528	3,524	10,483	9,075
Operating income (loss)	29,806	17,971	63,509	50,676
State Enterprise
Segment Reporting Information [Line Items]
Revenues	91,475	73,257	243,690	217,981
Payments
Segment Reporting Information [Line Items]
Revenues	11,266	9,736	30,996	28,973
All Other Software And Services
Segment Reporting Information [Line Items]
Revenues	31,849	7,392	44,612	20,178
Operating Segments | State Enterprise
Segment Reporting Information [Line Items]
Revenues	91,475	73,257	243,690	217,981
Costs & expenses	53,807	43,821	145,954	130,881
Depreciation & amortization	653	721	2,035	2,005
Operating income (loss)	37,015	28,715	95,701	85,095
Operating Segments | Payments
Segment Reporting Information [Line Items]
Revenues	11,266	9,736	30,996	28,973
Costs & expenses	8,788	7,271	24,331	22,508
Depreciation & amortization	1	0	4	2
Operating income (loss)	2,477	2,465	6,661	6,463
Operating Segments | All Other Software And Services
Segment Reporting Information [Line Items]
Revenues	31,849	7,392	44,612	20,178
Costs & expenses	22,502	2,902	28,028	7,586
Depreciation & amortization	1,150	359	3,335	576
Operating income (loss)	8,197	4,131	13,249	12,016
Other Reconciling Items
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Costs & expenses	16,159	14,896	46,993	46,406
Depreciation & amortization	1,724	2,444	5,109	6,492
Operating income (loss)	$ (17,883)	$ (17,340)	$ (52,102)	$ (52,898)