DEFERRED REVENUE AND PERFORMANCE OBLIGATIONS - Deferred Revenue (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Disaggregation of Revenue
Deferred revenue	$ 461,378
Contract With Customer Liability
Balance at beginning of year	412,694
Deferral of revenue	1,094,185
Recognition of deferred revenue	(1,045,501)
Balance at end of year	461,378
Operating segments | Enterprise Software
Disaggregation of Revenue
Deferred revenue	375,838
Contract With Customer Liability
Balance at beginning of year	375,838
Balance at end of year	422,742
Operating segments | Appraisal and Tax
Disaggregation of Revenue
Deferred revenue	35,487
Contract With Customer Liability
Balance at beginning of year	35,487
Balance at end of year	36,945
Corporate
Disaggregation of Revenue
Deferred revenue	1,369
Contract With Customer Liability
Balance at beginning of year	1,369
Balance at end of year	$ 1,691