Segment and Related Information - Schedule of Segment Revenues and Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 275,124	$ 236,060	$ 522,190	$ 457,234
Operating income	36,666	37,142	71,157	75,980
Intercompany
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intercompany | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	3,660	3,086	7,213	6,322
Intercompany | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intercompany | Corporate
Segment Reporting Information [Line Items]
Revenue	(3,660)	(3,086)	(7,213)	(6,322)
Operating segments | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	247,632	212,235	475,007	414,747
Operating income	61,391	58,417	118,425	115,032
Operating segments | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	24,999	22,299	48,246	43,859
Operating income	6,200	5,502	11,735	10,149
Corporate
Segment Reporting Information [Line Items]
Revenue	2,493
Operating income	(17,671)	(17,012)	(34,217)	(30,739)
Corporate and Eliminations
Segment Reporting Information [Line Items]
Revenue	2,493	1,526	(1,063)	(1,372)
Corporate and Eliminations | Corporate
Segment Reporting Information [Line Items]
Revenue		1,526	(1,063)	(1,372)
Operating segment and corporate non-segment
Segment Reporting Information [Line Items]
Revenue	275,124	236,060	522,190	457,234
Operating income	49,920	46,907	95,943	94,442
Software licenses and royalties
Segment Reporting Information [Line Items]
Revenue	20,675	22,400	42,468	45,176
Software licenses and royalties | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	17,983	19,991	36,994	40,680
Software licenses and royalties | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	2,692	2,409	5,474	4,496
Software licenses and royalties | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Subscriptions
Segment Reporting Information [Line Items]
Revenue	73,475	53,009	140,750	102,037
Subscriptions | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	70,867	50,637	135,509	97,321
Subscriptions | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	2,608	2,372	5,241	4,716
Subscriptions | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Software services
Segment Reporting Information [Line Items]
Revenue	57,401	50,674	105,844	96,613
Software services | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	50,141	45,002	92,108	85,289
Software services | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	7,260	5,672	13,736	11,324
Software services | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Maintenance
Segment Reporting Information [Line Items]
Revenue	106,689	96,076	206,841	189,973
Maintenance | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	100,483	89,795	194,495	177,609
Maintenance | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	6,206	6,281	12,346	12,364
Maintenance | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Appraisal services
Segment Reporting Information [Line Items]
Revenue	6,233	5,532	11,447	10,926
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	6,233	5,532	11,447	10,926
Appraisal services | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Hardware and other
Segment Reporting Information [Line Items]
Revenue	10,651	8,369	14,840	12,509
Hardware and other | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	4,498	3,724	8,688	7,526
Hardware and other | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	0	33	2	33
Hardware and other | Corporate
Segment Reporting Information [Line Items]
Revenue	$ 6,153	$ 4,612	$ 6,150	$ 4,950