Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue
Total revenues	$ 285,746	$ 275,400	$ 833,378	$ 797,590
Intercompany
Disaggregation of Revenue
Total revenues	(5,166)	(4,029)	(13,720)	(11,242)
Intercompany | Enterprise Software
Disaggregation of Revenue
Total revenues	5,128	3,995	13,662	11,055
Intercompany | Appraisal and Tax
Disaggregation of Revenue
Total revenues	38	34	58	187
Operating segments | Enterprise Software
Disaggregation of Revenue
Total revenues	261,939	246,940	759,995	709,030
Operating segments | Appraisal and Tax
Disaggregation of Revenue
Total revenues	28,973	32,503	87,101	93,666
Corporate
Disaggregation of Revenue
Total revenues	(5,166)	(4,043)	(13,718)	(5,106)
Corporate and Elimination
Disaggregation of Revenue
Total revenues	(5,166)	(4,043)	(13,718)	(5,106)
Recurring revenues
Disaggregation of Revenue
Total revenues	207,268	185,105	605,754	532,696
Recurring revenues | Enterprise Software
Disaggregation of Revenue
Total revenues	191,242	171,352	559,191	492,822
Recurring revenues | Appraisal and Tax
Disaggregation of Revenue
Total revenues	16,026	13,753	46,563	39,874
Recurring revenues | Corporate
Disaggregation of Revenue
Total revenues	0	0	0	0
Non-recurring revenues
Disaggregation of Revenue
Total revenues	78,478	90,295	227,624	264,894
Non-recurring revenues | Enterprise Software
Disaggregation of Revenue
Total revenues	65,569	71,593	187,142	205,153
Non-recurring revenues | Appraisal and Tax
Disaggregation of Revenue
Total revenues	12,909	18,716	40,480	53,605
Non-recurring revenues | Corporate
Disaggregation of Revenue
Total revenues	0	(14)	2	6,136
Software licenses and royalties
Disaggregation of Revenue
Total revenues	19,937	25,379	55,699	67,847
Software licenses and royalties | Enterprise Software
Disaggregation of Revenue
Total revenues	17,798	22,954	48,432	59,031
Software licenses and royalties | Appraisal and Tax
Disaggregation of Revenue
Total revenues	2,139	2,425	7,267	8,816
Software licenses and royalties | Corporate
Disaggregation of Revenue
Total revenues	0	0	0	0
Subscriptions
Disaggregation of Revenue
Total revenues	89,290	75,272	256,651	216,022
Subscriptions | Enterprise Software
Disaggregation of Revenue
Total revenues	82,972	70,833	238,744	203,474
Subscriptions | Appraisal and Tax
Disaggregation of Revenue
Total revenues	6,318	4,439	17,907	12,548
Subscriptions | Corporate
Disaggregation of Revenue
Total revenues	0	0	0	0
Software services
Disaggregation of Revenue
Total revenues	47,946	54,997	143,733	160,841
Software services | Enterprise Software
Disaggregation of Revenue
Total revenues	42,640	44,752	126,488	133,612
Software services | Appraisal and Tax
Disaggregation of Revenue
Total revenues	5,306	10,245	17,245	27,229
Software services | Corporate
Disaggregation of Revenue
Total revenues	0	0	0	0
Maintenance
Disaggregation of Revenue
Total revenues	117,979	109,833	349,104	316,674
Maintenance | Enterprise Software
Disaggregation of Revenue
Total revenues	108,270	100,519	320,447	289,348
Maintenance | Appraisal and Tax
Disaggregation of Revenue
Total revenues	9,709	9,314	28,657	27,326
Maintenance | Corporate
Disaggregation of Revenue
Total revenues	0	0	0	0
Appraisal services
Disaggregation of Revenue
Total revenues	5,394	6,008	15,853	17,455
Appraisal services | Enterprise Software
Disaggregation of Revenue
Total revenues	0	0	0	0
Appraisal services | Appraisal and Tax
Disaggregation of Revenue
Total revenues	5,394	6,008	15,853	17,455
Appraisal services | Corporate
Disaggregation of Revenue
Total revenues	0	0	0	0
Hardware and other
Disaggregation of Revenue
Total revenues	5,200	3,911	12,338	18,751
Hardware and other | Enterprise Software
Disaggregation of Revenue
Total revenues	5,131	3,887	12,222	12,510
Hardware and other | Appraisal and Tax
Disaggregation of Revenue
Total revenues	69	38	114	105
Hardware and other | Corporate
Disaggregation of Revenue
Total revenues	0	(14)	2	6,136
Products and services transferred at a point in time
Disaggregation of Revenue
Total revenues	21,977	25,273	59,649	72,825
Products and services transferred at a point in time | Software licenses and royalties
Disaggregation of Revenue
Total revenues	16,777	21,362	47,311	54,074
Products and services transferred at a point in time | Subscriptions
Disaggregation of Revenue
Total revenues	0	0	0
Products and services transferred at a point in time | Software services
Disaggregation of Revenue
Total revenues	0	0	0	0
Products and services transferred at a point in time | Maintenance
Disaggregation of Revenue
Total revenues	0	0	0	0
Products and services transferred at a point in time | Appraisal services
Disaggregation of Revenue
Total revenues	0	0	0	0
Products and services transferred at a point in time | Hardware and other
Disaggregation of Revenue
Total revenues	5,200	3,911	12,338	18,751
Products and services transferred over time
Disaggregation of Revenue
Total revenues	263,769	250,127	773,729	724,765
Products and services transferred over time | Software licenses and royalties
Disaggregation of Revenue
Total revenues	3,160	4,017	8,388	13,773
Products and services transferred over time | Subscriptions
Disaggregation of Revenue
Total revenues	89,290	75,272	256,651	216,022
Products and services transferred over time | Software services
Disaggregation of Revenue
Total revenues	47,946	54,997	143,733	160,841
Products and services transferred over time | Maintenance
Disaggregation of Revenue
Total revenues	117,979	109,833	349,104	316,674
Products and services transferred over time | Appraisal services
Disaggregation of Revenue
Total revenues	5,394	6,008	15,853	17,455
Products and services transferred over time | Hardware and other
Disaggregation of Revenue
Total revenues	$ 0	$ 0	$ 0	$ 0