Deferred Revenue and Performance Obligations - Deferred Revenue (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 391,801
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	350,936
Deferral of revenue	691,512
Recognition of deferred revenue	(650,647)
Balance, end of period	391,801
Operating segments | Enterprise Software
Disaggregation of Revenue [Line Items]
Deferred revenue	367,416
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	327,521
Balance, end of period	367,416
Operating segments | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Deferred revenue	23,224
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	20,018
Balance, end of period	23,224
Corporate
Disaggregation of Revenue [Line Items]
Deferred revenue	1,161
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	3,397
Balance, end of period	$ 1,161