Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 275,400	$ 236,067	$ 797,590	$ 693,301
Operating segments | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	253,535	215,848	728,542	630,595
Operating segments | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	25,908	23,625	74,154	67,485
Intercompany
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Intercompany | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	4,029	3,373	11,242	9,696
Intercompany | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Intercompany | Corporate
Disaggregation of Revenue [Line Items]
Revenue	(4,029)	(3,373)	(11,242)	(9,696)
Corporate and Elimination
Disaggregation of Revenue [Line Items]
Revenue	(4,043)	(3,406)	(5,106)	(4,779)
Corporate and Elimination | Corporate
Disaggregation of Revenue [Line Items]
Revenue	(4,043)	(3,406)	(5,106)	(4,779)
Recurring revenues
Disaggregation of Revenue [Line Items]
Revenue	185,105	154,914	532,696	446,924
Recurring revenues | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	175,836	146,292	505,840	421,222
Recurring revenues | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	9,269	8,622	26,856	25,702
Recurring revenues | Corporate
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Non-recurring revenues
Disaggregation of Revenue [Line Items]
Revenue	90,295	81,153	264,894	246,377
Non-recurring revenues | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	73,670	66,183	211,460	199,677
Non-recurring revenues | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	16,639	15,003	47,298	41,783
Non-recurring revenues | Corporate
Disaggregation of Revenue [Line Items]
Revenue	(14)	(33)	6,136	4,917
Software licenses and royalties
Disaggregation of Revenue [Line Items]
Revenue	25,379	22,444	67,847	67,620
Software licenses and royalties | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	23,449	19,544	60,443	60,224
Software licenses and royalties | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	1,930	2,900	7,404	7,396
Software licenses and royalties | Corporate
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Subscriptions
Disaggregation of Revenue [Line Items]
Revenue	75,272	58,699	216,022	160,736
Subscriptions | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	72,398	56,220	207,907	153,541
Subscriptions | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	2,874	2,479	8,115	7,195
Subscriptions | Corporate
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Software services
Disaggregation of Revenue [Line Items]
Revenue	54,997	48,199	160,841	144,812
Software services | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	46,296	41,640	138,404	126,928
Software services | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	8,701	6,559	22,437	17,884
Software services | Corporate
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Maintenance
Disaggregation of Revenue [Line Items]
Revenue	109,833	96,215	316,674	286,188
Maintenance | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	103,438	90,072	297,933	267,681
Maintenance | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	6,395	6,143	18,741	18,507
Maintenance | Corporate
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Appraisal services
Disaggregation of Revenue [Line Items]
Revenue	6,008	5,544	17,455	16,470
Appraisal services | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Appraisal services | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	6,008	5,544	17,455	16,470
Appraisal services | Corporate
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Hardware and other
Disaggregation of Revenue [Line Items]
Revenue	3,911	4,966	18,751	17,475
Hardware and other | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	3,925	4,999	12,613	12,525
Hardware and other | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	0	0	2	33
Hardware and other | Corporate
Disaggregation of Revenue [Line Items]
Revenue	(14)	(33)	6,136	4,917
Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue	25,273	22,339	72,825	71,172
Products and services transferred at a point in time | Software licenses and royalties
Disaggregation of Revenue [Line Items]
Revenue	21,362	17,373	54,074	53,697
Products and services transferred at a point in time | Subscriptions
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Products and services transferred at a point in time | Software services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Products and services transferred at a point in time | Maintenance
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Products and services transferred at a point in time | Appraisal services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Products and services transferred at a point in time | Hardware and other
Disaggregation of Revenue [Line Items]
Revenue	3,911	4,966	18,751	17,475
Products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue	250,127	213,728	724,765	622,129
Products and services transferred over time | Software licenses and royalties
Disaggregation of Revenue [Line Items]
Revenue	4,017	5,071	13,773	13,923
Products and services transferred over time | Subscriptions
Disaggregation of Revenue [Line Items]
Revenue	75,272	58,699	216,022	160,736
Products and services transferred over time | Software services
Disaggregation of Revenue [Line Items]
Revenue	54,997	48,199	160,841	144,812
Products and services transferred over time | Maintenance
Disaggregation of Revenue [Line Items]
Revenue	109,833	96,215	316,674	286,188
Products and services transferred over time | Appraisal services
Disaggregation of Revenue [Line Items]
Revenue	6,008	5,544	17,455	16,470
Products and services transferred over time | Hardware and other
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0	$ 0	$ 0
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