Segment and Related Information - Schedule of Segment Revenues and Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information
Total revenues	$ 459,873	$ 285,746	$ 1,158,750	$ 833,378
Segment operating income	56,184	49,656	132,683	124,890
Software licenses and royalties
Segment Reporting Information
Total revenues	22,673	19,937	55,210	55,699
Subscriptions
Segment Reporting Information
Total revenues	252,942	89,290	554,979	256,651
Software services
Segment Reporting Information
Total revenues	54,624	47,946	155,601	143,733
Maintenance
Segment Reporting Information
Total revenues	117,833	117,979	356,566	349,104
Appraisal services
Segment Reporting Information
Total revenues	7,146	5,394	19,876	15,853
Hardware and other
Segment Reporting Information
Total revenues	4,655	5,200	16,518	12,338
Enterprise Software | Software licenses and royalties
Segment Reporting Information
Total revenues	21,238	17,798	50,064	48,432
Enterprise Software | Subscriptions
Segment Reporting Information
Total revenues	102,285	82,972	295,523	238,744
Enterprise Software | Software services
Segment Reporting Information
Total revenues	41,985	42,640	127,517	126,488
Enterprise Software | Maintenance
Segment Reporting Information
Total revenues	110,231	108,270	330,024	320,447
Enterprise Software | Appraisal services
Segment Reporting Information
Total revenues	0	0	0	0
Enterprise Software | Hardware and other
Segment Reporting Information
Total revenues	4,558	5,131	13,412	12,222
Appraisal and Tax | Software licenses and royalties
Segment Reporting Information
Total revenues	1,435	2,139	5,146	7,267
Appraisal and Tax | Subscriptions
Segment Reporting Information
Total revenues	8,311	6,318	23,829	17,907
Appraisal and Tax | Software services
Segment Reporting Information
Total revenues	4,603	5,306	14,405	17,245
Appraisal and Tax | Maintenance
Segment Reporting Information
Total revenues	7,399	9,709	26,184	28,657
Appraisal and Tax | Appraisal services
Segment Reporting Information
Total revenues	7,146	5,394	19,876	15,853
Appraisal and Tax | Hardware and other
Segment Reporting Information
Total revenues	9	69	79	114
NIC | Software licenses and royalties
Segment Reporting Information
Total revenues	0	0	0	0
NIC | Subscriptions
Segment Reporting Information
Total revenues	142,346	0	235,627	0
NIC | Software services
Segment Reporting Information
Total revenues	8,036	0	13,679	0
NIC | Maintenance
Segment Reporting Information
Total revenues	203	0	358	0
NIC | Appraisal services
Segment Reporting Information
Total revenues	0	0	0	0
NIC | Hardware and other
Segment Reporting Information
Total revenues	0	0	0	0
Intercompany
Segment Reporting Information
Total revenues	(5,143)	(5,166)	(16,040)	(13,720)
Intercompany | Enterprise Software
Segment Reporting Information
Total revenues	5,123	5,128	15,989	13,662
Intercompany | Appraisal and Tax
Segment Reporting Information
Total revenues	20	38	51	58
Intercompany | NIC
Segment Reporting Information
Total revenues	0	0	0	0
Operating segments | Enterprise Software
Segment Reporting Information
Total revenues	285,420	261,939	832,529	759,995
Segment operating income	97,378	92,964	284,813	248,711
Operating segments | Appraisal and Tax
Segment Reporting Information
Total revenues	28,923	28,973	89,570	87,101
Segment operating income	6,928	9,938	24,876	26,246
Operating segments | NIC
Segment Reporting Information
Total revenues	150,585	0	249,664	0
Segment operating income	34,586	0	57,517	0
Corporate
Segment Reporting Information
Total revenues	(5,055)	(5,166)	(13,013)	(13,718)
Segment operating income	(55,629)	(39,889)	(170,825)	(109,893)
Corporate | Software licenses and royalties
Segment Reporting Information
Total revenues	0	0	0	0
Corporate | Subscriptions
Segment Reporting Information
Total revenues	0	0	0	0
Corporate | Software services
Segment Reporting Information
Total revenues	0	0	0	0
Corporate | Maintenance
Segment Reporting Information
Total revenues	0	0	0	0
Corporate | Appraisal services
Segment Reporting Information
Total revenues	0	0	0	0
Corporate | Hardware and other
Segment Reporting Information
Total revenues	88	0	3,027	2
Operating segment and corporate non-segment
Segment Reporting Information
Segment operating income	$ 83,263	$ 63,013	$ 196,381	$ 165,064