Segment and Related Information - Schedule of Segment Revenues and Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 236,060	$ 208,763	$ 457,234	$ 408,492
Operating Income	37,142	37,298	75,980	74,129
Intercompany | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	3,086	2,486	6,322	4,649
Intercompany | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Corporate and Elimination
Segment Reporting Information [Line Items]
Revenue	1,526	2,138	(1,372)	(25)
Operating segment and corporate non-segment
Segment Reporting Information [Line Items]
Operating Income	46,907	45,989	94,442	91,555
Operating segments | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	212,235	186,829	414,747	369,627
Operating Income	58,417	54,036	115,032	106,524
Operating segments | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	22,299	19,796	43,859	38,890
Operating Income	5,502	4,595	10,149	8,921
Corporate
Segment Reporting Information [Line Items]
Operating Income	(17,012)	(12,642)	(30,739)	(23,890)
Software licenses and royalties
Segment Reporting Information [Line Items]
Revenue	22,400	19,306	45,176	41,064
Software licenses and royalties | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	19,991	17,553	40,680	37,662
Software licenses and royalties | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	2,409	1,753	4,496	3,402
Software licenses and royalties | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Subscriptions
Segment Reporting Information [Line Items]
Revenue	53,009	40,517	102,037	80,379
Subscriptions | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	50,637	38,621	97,321	76,695
Subscriptions | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	2,372	1,896	4,716	3,684
Subscriptions | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Software services
Segment Reporting Information [Line Items]
Revenue	50,674	45,860	96,613	88,356
Software services | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	45,002	41,184	85,289	79,329
Software services | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	5,672	4,676	11,324	9,027
Software services | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Maintenance
Segment Reporting Information [Line Items]
Revenue	96,076	88,811	189,973	175,118
Maintenance | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	89,795	83,706	177,609	165,319
Maintenance | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	6,281	5,105	12,364	9,799
Maintenance | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Appraisal services
Segment Reporting Information [Line Items]
Revenue	5,532	6,366	10,926	12,978
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	5,532	6,366	10,926	12,978
Appraisal services | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Hardware and other
Segment Reporting Information [Line Items]
Revenue	8,369	7,903	12,509	10,597
Hardware and other | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	3,724	3,279	7,526	5,973
Hardware and other | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	33	0	33	0
Hardware and other | Corporate
Segment Reporting Information [Line Items]
Revenue	$ 4,612	$ 4,624	$ 4,950	$ 4,624