Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 221,174	$ 199,729
Operating segments | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	202,508	182,799
Operating segments | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	21,563	19,093
Intercompany
Disaggregation of Revenue [Line Items]
Revenue	(3,237)	(2,163)
Intercompany | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	(3,237)	(2,163)
Intercompany | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	0	0
Corporate and Elimination
Disaggregation of Revenue [Line Items]
Revenue	(2,897)	(2,163)
Recurring revenues
Disaggregation of Revenue [Line Items]
Revenue	142,925	126,169
Recurring revenues | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	134,496	119,687
Recurring revenues | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	8,429	6,482
Recurring revenues | Corporate
Disaggregation of Revenue [Line Items]
Revenue	0	0
Non-recurring revenues
Disaggregation of Revenue [Line Items]
Revenue	78,249	73,560
Non-recurring revenues | Enterprise Software
Disaggregation of Revenue [Line Items]
Revenue	64,775	60,949
Non-recurring revenues | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Revenue	13,134	12,611
Non-recurring revenues | Corporate
Disaggregation of Revenue [Line Items]
Revenue	340	0
Software licenses and royalties
Disaggregation of Revenue [Line Items]
Revenue	22,776	21,758
Subscriptions
Disaggregation of Revenue [Line Items]
Revenue	49,028	39,862
Software services
Disaggregation of Revenue [Line Items]
Revenue	45,939	42,496
Maintenance
Disaggregation of Revenue [Line Items]
Revenue	93,897	86,307
Appraisal services
Disaggregation of Revenue [Line Items]
Revenue	5,394	6,612
Hardware and other
Disaggregation of Revenue [Line Items]
Revenue	4,140	2,694
Products and services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue	23,203	19,809
Products and services transferred at a point in time | Software licenses and royalties
Disaggregation of Revenue [Line Items]
Revenue	19,063	17,115
Products and services transferred at a point in time | Subscriptions
Disaggregation of Revenue [Line Items]
Revenue	0	0
Products and services transferred at a point in time | Software services
Disaggregation of Revenue [Line Items]
Revenue	0	0
Products and services transferred at a point in time | Maintenance
Disaggregation of Revenue [Line Items]
Revenue	0	0
Products and services transferred at a point in time | Appraisal services
Disaggregation of Revenue [Line Items]
Revenue	0	0
Products and services transferred at a point in time | Hardware and other
Disaggregation of Revenue [Line Items]
Revenue	4,140	2,694
Products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue	197,971	179,920
Products and services transferred over time | Software licenses and royalties
Disaggregation of Revenue [Line Items]
Revenue	3,713	4,643
Products and services transferred over time | Subscriptions
Disaggregation of Revenue [Line Items]
Revenue	49,028	39,862
Products and services transferred over time | Software services
Disaggregation of Revenue [Line Items]
Revenue	45,939	42,496
Products and services transferred over time | Maintenance
Disaggregation of Revenue [Line Items]
Revenue	93,897	86,307
Products and services transferred over time | Appraisal services
Disaggregation of Revenue [Line Items]
Revenue	5,394	6,612
Products and services transferred over time | Hardware and other
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0
Minimum
Disaggregation of Revenue [Line Items]
Contract term	1 year
Typical contract term	3 years
Minimum | Appraisal services
Disaggregation of Revenue [Line Items]
Contract term	1 year
Maximum
Disaggregation of Revenue [Line Items]
Contract term	10 years
Typical contract term	5 years
Maximum | Appraisal services
Disaggregation of Revenue [Line Items]
Contract term	3 years