Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue
Total Revenue	$ 276,541	$ 247,066
Operating segments | Enterprise Software
Disaggregation of Revenue
Total Revenue	250,177	221,035
Operating segments | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	30,381	29,587
Intercompany
Disaggregation of Revenue
Total Revenue	(4,019)	(3,553)
Intercompany | Enterprise Software
Disaggregation of Revenue
Total Revenue	4,001	3,484
Intercompany | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	18	69
Corporate
Disaggregation of Revenue
Total Revenue	(4,017)	(3,556)
Corporate and Elimination
Disaggregation of Revenue
Total Revenue	(4,017)	(3,556)
Recurring revenues
Disaggregation of Revenue
Total Revenue	196,088	167,427
Recurring revenues | Enterprise Software
Disaggregation of Revenue
Total Revenue	181,485	154,443
Recurring revenues | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	14,603	12,984
Recurring revenues | Corporate
Disaggregation of Revenue
Total Revenue	0	0
Non-recurring revenues
Disaggregation of Revenue
Total Revenue	80,453	79,639
Non-recurring revenues | Enterprise Software
Disaggregation of Revenue
Total Revenue	64,691	63,108
Non-recurring revenues | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	15,760	16,534
Non-recurring revenues | Corporate
Disaggregation of Revenue
Total Revenue	2	(3)
Software licenses and royalties
Disaggregation of Revenue
Total Revenue	18,737	21,793
Software licenses and royalties | Enterprise Software
Disaggregation of Revenue
Total Revenue	15,951	18,522
Software licenses and royalties | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	2,786	3,271
Software licenses and royalties | Corporate
Disaggregation of Revenue
Total Revenue	0	0
Subscriptions
Disaggregation of Revenue
Total Revenue	81,723	67,275
Subscriptions | Enterprise Software
Disaggregation of Revenue
Total Revenue	76,644	63,255
Subscriptions | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	5,079	4,020
Subscriptions | Corporate
Disaggregation of Revenue
Total Revenue	0	0
Software services
Disaggregation of Revenue
Total Revenue	52,133	48,443
Software services | Enterprise Software
Disaggregation of Revenue
Total Revenue	44,949	40,456
Software services | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	7,184	7,987
Software services | Corporate
Disaggregation of Revenue
Total Revenue	0	0
Maintenance
Disaggregation of Revenue
Total Revenue	114,365	100,152
Maintenance | Enterprise Software
Disaggregation of Revenue
Total Revenue	104,841	91,188
Maintenance | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	9,524	8,964
Maintenance | Corporate
Disaggregation of Revenue
Total Revenue	0	0
Appraisal services
Disaggregation of Revenue
Total Revenue	5,763	5,214
Appraisal services | Enterprise Software
Disaggregation of Revenue
Total Revenue	0	0
Appraisal services | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	5,763	5,214
Appraisal services | Corporate
Disaggregation of Revenue
Total Revenue	0	0
Hardware and other
Disaggregation of Revenue
Total Revenue	3,820	4,189
Hardware and other | Enterprise Software
Disaggregation of Revenue
Total Revenue	3,791	4,130
Hardware and other | Appraisal and Tax
Disaggregation of Revenue
Total Revenue	27	62
Hardware and other | Corporate
Disaggregation of Revenue
Total Revenue	2	(3)
Products and services transferred at a point in time
Disaggregation of Revenue
Total Revenue	19,886	21,099
Products and services transferred at a point in time | Software licenses and royalties
Disaggregation of Revenue
Total Revenue	16,066	16,910
Products and services transferred at a point in time | Subscriptions
Disaggregation of Revenue
Total Revenue	0	0
Products and services transferred at a point in time | Software services
Disaggregation of Revenue
Total Revenue	0	0
Products and services transferred at a point in time | Maintenance
Disaggregation of Revenue
Total Revenue	0	0
Products and services transferred at a point in time | Appraisal services
Disaggregation of Revenue
Total Revenue	0	0
Products and services transferred at a point in time | Hardware and other
Disaggregation of Revenue
Total Revenue	3,820	4,189
Products and services transferred over time
Disaggregation of Revenue
Total Revenue	256,655	225,967
Products and services transferred over time | Software licenses and royalties
Disaggregation of Revenue
Total Revenue	2,671	4,883
Products and services transferred over time | Subscriptions
Disaggregation of Revenue
Total Revenue	81,723	67,275
Products and services transferred over time | Software services
Disaggregation of Revenue
Total Revenue	52,133	48,443
Products and services transferred over time | Maintenance
Disaggregation of Revenue
Total Revenue	114,365	100,152
Products and services transferred over time | Appraisal services
Disaggregation of Revenue
Total Revenue	5,763	5,214
Products and services transferred over time | Hardware and other
Disaggregation of Revenue
Total Revenue	$ 0	$ 0