Accounting Standards and Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 321.8	$ 314.9
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Typical contract term	3 years
Contract term	1 year
Accounts receivable payment term	30 days
Sales commissions amortization period	3 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Typical contract term	5 years
Contract term	10 years
Sales commissions amortization period	7 years
Subscription - Hosting Services | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract term	1 year
Appraisal services | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract term	1 year
Appraisal services | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract term	3 years
Unbilled Revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 113.1	104.2
Retention Receivable | Unbilled Revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 13.4	$ 12.2