Deferred Revenue and Performance Obligations - Deferred Revenue (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 412,694
Contract With Customer Liability [Roll Forward]
Balance at beginning of year	350,936
Deferral of revenue	993,109
Recognition of deferred revenue	(931,351)
Balance at end of year	412,694
Operating segments | Enterprise Software
Disaggregation of Revenue [Line Items]
Deferred revenue	327,521
Contract With Customer Liability [Roll Forward]
Balance at beginning of year	327,521
Balance at end of year	386,115
Operating segments | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Deferred revenue	20,018
Contract With Customer Liability [Roll Forward]
Balance at beginning of year	20,018
Balance at end of year	25,210
Corporate
Disaggregation of Revenue [Line Items]
Deferred revenue	3,397
Contract With Customer Liability [Roll Forward]
Balance at beginning of year	3,397
Balance at end of year	$ 1,369