Segment and Related Information - Schedule of Segment Revenues and Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 236,067	$ 214,706	$ 693,301	$ 623,198
Operating income	37,585	44,282	113,565	118,411
Operating segments | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	215,848	196,552	630,595	566,179
Operating income	59,334	61,243	174,365	167,767
Operating segments | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	23,625	20,816	67,485	59,706
Operating income	6,695	5,450	16,845	14,371
Intercompany | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	3,373	2,660	9,696	7,309
Intercompany | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Intercompany | Corporate
Segment Reporting Information [Line Items]
Revenue	(3,373)	(2,660)	(9,696)	(7,309)
Corporate
Segment Reporting Information [Line Items]
Operating income	(18,161)	(13,578)	(48,900)	(37,468)
Operating segment and corporate non-segment
Segment Reporting Information [Line Items]
Operating income	47,868	53,115	142,310	144,670
Software licenses and royalties
Segment Reporting Information [Line Items]
Revenue	22,444	22,762	67,620	63,826
Software licenses and royalties | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	19,544	21,143	60,224	58,805
Software licenses and royalties | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	2,900	1,619	7,396	5,021
Software licenses and royalties | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Subscriptions
Segment Reporting Information [Line Items]
Revenue	58,699	44,352	160,736	124,731
Subscriptions | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	56,220	42,338	153,541	119,033
Subscriptions | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	2,479	2,014	7,195	5,698
Subscriptions | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Software services
Segment Reporting Information [Line Items]
Revenue	48,199	46,045	144,812	134,401
Software services | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	41,640	40,861	126,928	120,190
Software services | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	6,559	5,184	17,884	14,211
Software services | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Maintenance
Segment Reporting Information [Line Items]
Revenue	96,215	91,847	286,188	266,965
Maintenance | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	90,072	86,138	267,681	251,457
Maintenance | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	6,143	5,709	18,507	15,508
Maintenance | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Appraisal services
Segment Reporting Information [Line Items]
Revenue	5,544	6,290	16,470	19,268
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	5,544	6,290	16,470	19,268
Appraisal services | Corporate
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Hardware and other
Segment Reporting Information [Line Items]
Revenue	4,966	3,410	17,475	14,007
Hardware and other | Enterprise Software
Segment Reporting Information [Line Items]
Revenue	4,999	3,412	12,525	9,385
Hardware and other | Appraisal and Tax
Segment Reporting Information [Line Items]
Revenue	0	0	33	0
Hardware and other | Corporate
Segment Reporting Information [Line Items]
Revenue	$ (33)	$ (2)	$ 4,917	$ 4,622