Deferred Revenue and Performance Obligations - Deferred Revenue (Details) $ in Thousands	6 Months Ended
	Jun. 30, 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	460,351
Recognition of deferred revenue	(442,248)
Balance, end of period	369,039
Operating segments | Enterprise Software
Disaggregation of Revenue [Line Items]
Deferred revenue	346,583
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	327,521
Balance, end of period	346,583
Operating segments | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Deferred revenue	22,456
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	20,018
Balance, end of period	22,456
Corporate
Disaggregation of Revenue [Line Items]
Deferred revenue	0
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2018	3,397
Balance, end of period	$ 0