Deferred Revenue and Performance Obligations -Deferred Revenue (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jan. 01, 2017
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 299,887	$ 316,869	$ 290,100
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2017 (As Adjusted).	299,887
Deferral of revenue	414,396
Recognition of deferred revenue	(397,414)
Balance, end of period	316,869
Remaining performance obligations		1,200,000
Operating segments | Enterprise Software
Disaggregation of Revenue [Line Items]
Deferred revenue	277,198	299,332
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2017 (As Adjusted).	277,198
Balance, end of period	299,332
Operating segments | Appraisal and Tax
Disaggregation of Revenue [Line Items]
Deferred revenue	20,387	15,199
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2017 (As Adjusted).	20,387
Balance, end of period	15,199
Corporate
Disaggregation of Revenue [Line Items]
Deferred revenue	2,302	$ 2,338
Contract With Customer Liability [Roll Forward]
Balance, beginning of period December 31, 2017 (As Adjusted).	2,302
Balance, end of period	$ 2,338