Deferred Revenue and Performance Obligations - Deferred Revenue (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Disaggregation of Revenue
Deferred revenue	$ 495,303
Contract With Customer Liability
Beginning balance	461,378
Deferral of revenue	868,125
Recognition of deferred revenue	(834,200)
Ending balance	495,303
Operating segments | Enterprise Software
Disaggregation of Revenue
Deferred revenue	452,435
Contract With Customer Liability
Beginning balance	422,742
Ending balance	452,435
Operating segments | Appraisal and Tax
Disaggregation of Revenue
Deferred revenue	31,300
Contract With Customer Liability
Beginning balance	36,945
Ending balance	31,300
Operating segments | NIC
Disaggregation of Revenue
Deferred revenue	9,525
Contract With Customer Liability
Beginning balance	0
Ending balance	9,525
Corporate
Disaggregation of Revenue
Deferred revenue	2,043
Contract With Customer Liability
Beginning balance	1,691
Ending balance	$ 2,043