Segment and Related Information - Schedule of Segment Revenues and Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 275,400	$ 236,067	$ 797,590	$ 693,301
Operating income	40,053	37,585	111,210	113,565
Intercompany
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intercompany | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	4,029	3,373	11,242	9,696
Intercompany | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intercompany | Corporate
Segment Reporting Information [Line Items]
Revenue	(4,029)	(3,373)	(11,242)	(9,696)
Operating segments | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	253,535	215,848	728,542	630,595
Operating income	64,140	59,334	182,565	174,365
Operating segments | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	25,908	23,625	74,154	67,485
Operating income	7,577	6,695	19,312	16,845
Corporate
Segment Reporting Information [Line Items]
Operating income	(18,043)	(18,161)	(52,260)	(48,900)
Corporate and Eliminations
Segment Reporting Information [Line Items]
Revenue	(4,043)	(3,406)	(5,106)	(4,779)
Corporate and Eliminations | Corporate
Segment Reporting Information [Line Items]
Revenue	(4,043)	(3,406)	(5,106)	(4,779)
Operating segment and corporate non-segment
Segment Reporting Information [Line Items]
Revenue	275,400	236,067	797,590	693,301
Operating income	53,674	47,868	149,617	142,310
Software licenses and royalties
Segment Reporting Information [Line Items]
Revenue	25,379	22,444	67,847	67,620
Software licenses and royalties | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	23,449	19,544	60,443	60,224
Software licenses and royalties | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	1,930	2,900	7,404	7,396
Software licenses and royalties | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Subscriptions
Segment Reporting Information [Line Items]
Revenue	75,272	58,699	216,022	160,736
Subscriptions | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	72,398	56,220	207,907	153,541
Subscriptions | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	2,874	2,479	8,115	7,195
Subscriptions | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Software services
Segment Reporting Information [Line Items]
Revenue	54,997	48,199	160,841	144,812
Software services | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	46,296	41,640	138,404	126,928
Software services | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	8,701	6,559	22,437	17,884
Software services | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Maintenance
Segment Reporting Information [Line Items]
Revenue	109,833	96,215	316,674	286,188
Maintenance | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	103,438	90,072	297,933	267,681
Maintenance | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	6,395	6,143	18,741	18,507
Maintenance | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Appraisal services
Segment Reporting Information [Line Items]
Revenue	6,008	5,544	17,455	16,470
Appraisal services | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Appraisal services | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	6,008	5,544	17,455	16,470
Appraisal services | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Hardware and other
Segment Reporting Information [Line Items]
Revenue	3,911	4,966	18,751	17,475
Hardware and other | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	3,925	4,999	12,613	12,525
Hardware and other | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	0	0	2	33
Hardware and other | Corporate
Segment Reporting Information [Line Items]
Revenue	$ (14)	$ (33)	$ 6,136	$ 4,917