Segment and Related Information - Schedule of Segment Revenues and Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information
Total revenues	$ 404,075	$ 271,091	$ 698,877	$ 547,632
Segment operating income	38,291	41,341	76,499	75,234
Software licenses and royalties
Segment Reporting Information
Total revenues	17,604	17,025	32,537	35,762
Subscriptions
Segment Reporting Information
Total revenues	199,558	85,638	302,037	167,361
Software services
Segment Reporting Information
Total revenues	53,337	43,654	100,977	95,787
Maintenance
Segment Reporting Information
Total revenues	119,621	116,760	238,733	231,125
Appraisal services
Segment Reporting Information
Total revenues	6,265	4,696	12,730	10,459
Hardware and other
Segment Reporting Information
Total revenues	7,690	3,318	11,863	7,138
Enterprise Software | Software licenses and royalties
Segment Reporting Information
Total revenues	15,779	14,683	28,826	30,634
Enterprise Software | Subscriptions
Segment Reporting Information
Total revenues	98,407	79,128	193,238	155,772
Enterprise Software | Software services
Segment Reporting Information
Total revenues	42,972	38,899	85,532	83,848
Enterprise Software | Maintenance
Segment Reporting Information
Total revenues	110,010	107,336	219,793	212,177
Enterprise Software | Appraisal services
Segment Reporting Information
Total revenues	0	0	0	0
Enterprise Software | Hardware and other
Segment Reporting Information
Total revenues	4,728	3,300	8,854	7,091
Appraisal and Tax | Software licenses and royalties
Segment Reporting Information
Total revenues	1,825	2,342	3,711	5,128
Appraisal and Tax | Subscriptions
Segment Reporting Information
Total revenues	7,870	6,510	15,518	11,589
Appraisal and Tax | Software services
Segment Reporting Information
Total revenues	4,722	4,755	9,802	11,939
Appraisal and Tax | Maintenance
Segment Reporting Information
Total revenues	9,456	9,424	18,785	18,948
Appraisal and Tax | Appraisal services
Segment Reporting Information
Total revenues	6,265	4,696	12,730	10,459
Appraisal and Tax | Hardware and other
Segment Reporting Information
Total revenues	23	18	70	45
NIC | Software licenses and royalties
Segment Reporting Information
Total revenues	0	0	0	0
NIC | Subscriptions
Segment Reporting Information
Total revenues	93,281	0	93,281	0
NIC | Software services
Segment Reporting Information
Total revenues	5,643	0	5,643	0
NIC | Maintenance
Segment Reporting Information
Total revenues	155	0	155	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	(5,621)	(4,535)	(10,897)	(8,554)
Intercompany | Enterprise Software
Segment Reporting Information
Total revenues	5,605	4,533	10,866	8,534
Intercompany | Appraisal and Tax
Segment Reporting Information
Total revenues	16	2	31	20
Intercompany | NIC
Segment Reporting Information
Total revenues	0	0	0	0
Operating segments | Enterprise Software
Segment Reporting Information
Total revenues	277,501	247,879	547,109	498,056
Segment operating income	94,561	82,080	187,435	155,747
Operating segments | Appraisal and Tax
Segment Reporting Information
Total revenues	30,177	27,747	60,647	58,128
Segment operating income	8,689	7,767	17,948	16,309
Operating segments | NIC
Segment Reporting Information
Total revenues	99,079	0	99,079	0
Segment operating income	22,931	0	22,931	0
Corporate
Segment Reporting Information
Total revenues	(2,682)	(4,535)	(7,958)	(8,552)
Segment operating income	(64,647)	(35,108)	(115,196)	(70,005)
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	2,939	0	2,939	2
Operating segment and corporate non-segment
Segment Reporting Information
Segment operating income	$ 61,534	$ 54,739	$ 113,118	$ 102,051