Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenues	$ 288,837	$ 275,400	$ 275,124	$ 247,066	$ 241,981	$ 236,067	$ 236,060	$ 221,174	$ 1,086,427	$ 935,282	$ 840,899
Intercompany
Disaggregation of Revenue [Line Items]
Total revenues									(15,496)	(13,155)	(10,425)
Corporate and Elimination
Disaggregation of Revenue [Line Items]
Total revenues									(9,240)	(8,274)	(5,813)
Enterprise Software | Intercompany
Disaggregation of Revenue [Line Items]
Total revenues									(15,496)	(13,155)	(10,425)
Enterprise Software | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									1,000,845	853,200	765,133
Appraisal and Tax | Intercompany
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Appraisal and Tax | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									94,822	90,356	81,579
Recurring revenues
Disaggregation of Revenue [Line Items]
Total revenues									726,670	605,069	531,495
Recurring revenues | Corporate
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Recurring revenues | Enterprise Software
Disaggregation of Revenue [Line Items]
Total revenues									690,156	570,645	502,018
Recurring revenues | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Total revenues									36,514	34,424	29,477
Non-recurring revenues
Disaggregation of Revenue [Line Items]
Total revenues									359,757	330,213	309,404
Non-recurring revenues | Corporate
Disaggregation of Revenue [Line Items]
Total revenues									6,256	4,881	4,612
Non-recurring revenues | Enterprise Software
Disaggregation of Revenue [Line Items]
Total revenues									295,193	269,400	252,690
Non-recurring revenues | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Total revenues									$ 58,308	55,932	52,102
Minimum
Disaggregation of Revenue [Line Items]
Contract term									1 year
Typical contract term									3 years
Maximum
Disaggregation of Revenue [Line Items]
Contract term									10 years
Typical contract term									5 years
Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues									$ 107,912	98,846	86,846
Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues									978,515	836,436	754,053
Software licenses and royalties
Disaggregation of Revenue [Line Items]
Total revenues									100,205	93,441	86,242
Software licenses and royalties | Corporate
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Software licenses and royalties | Enterprise Software | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									92,567	83,735	78,388
Software licenses and royalties | Appraisal and Tax | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									7,638	9,706	7,854
Software licenses and royalties | Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues									84,900	75,188	69,167
Software licenses and royalties | Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues									15,305	18,253	17,075
Subscriptions
Disaggregation of Revenue [Line Items]
Total revenues									296,352	220,547	172,176
Subscriptions | Corporate
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Subscriptions | Enterprise Software | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									285,092	210,740	164,317
Subscriptions | Appraisal and Tax | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									11,260	9,807	7,859
Subscriptions | Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Subscriptions | Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues									296,352	220,547	172,176
Software services
Disaggregation of Revenue [Line Items]
Total revenues									213,061	191,269	180,460
Software services | Corporate
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Software services | Enterprise Software | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									185,892	166,921	161,245
Software services | Appraisal and Tax | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									27,169	24,348	19,215
Software services | Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Software services | Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues									213,061	191,269	180,460
Maintenance
Disaggregation of Revenue [Line Items]
Total revenues									430,318	384,521	359,319
Maintenance | Corporate
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Maintenance | Enterprise Software | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									405,063	359,904	337,701
Maintenance | Appraisal and Tax | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									25,255	24,617	21,618
Maintenance | Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Maintenance | Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues									430,318	384,521	359,319
Appraisal services
Disaggregation of Revenue [Line Items]
Total revenues									23,479	21,846	25,023
Appraisal services | Corporate
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Appraisal services | Enterprise Software | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Appraisal services | Appraisal and Tax | Operating segments
Disaggregation of Revenue [Line Items]
Total revenues									$ 23,479	21,846	25,023
Appraisal services | Minimum
Disaggregation of Revenue [Line Items]
Contract term									1 year
Appraisal services | Maximum
Disaggregation of Revenue [Line Items]
Contract term									3 years
Appraisal services | Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues									$ 0	0	0
Appraisal services | Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues									23,479	21,846	25,023
Hardware and other
Disaggregation of Revenue [Line Items]
Total revenues									23,012	23,658	17,679
Hardware and other | Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues									23,012	23,658	17,679
Hardware and other | Products and services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues									$ 0	$ 0	$ 0