Deferred Revenue and Performance Obligations - Deferred Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 350,936
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	350,936
Deferral of revenue	167,975
Recognition of deferred revenue	(198,569)
Balance, end of period	320,342
Operating segments | Enterprise Software
Disaggregation of Revenue [Line Items]
Deferred revenue	298,184
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	327,521
Balance, end of period	298,184
Operating segments | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Deferred revenue	21,589
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	20,018
Balance, end of period	21,589
Corporate
Disaggregation of Revenue [Line Items]
Deferred revenue	569
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	3,397
Balance, end of period	$ 569