Acquisitions - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	Apr. 30, 2018	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill		$ 740,146	$ 740,146	$ 657,987
Revenue, actual		3,000
Income (loss), actual		$ (4,000)
Socrata, Inc.
Business Acquisition [Line Items]
Net cash acquired	$ 1,724
Payments to acquire business	147,600
Liability incurred	1,100
Tangible assets acquired	7,500
Liabilities assumed	(8,900)
Goodwill	78,909
Identifiable intangible assets	75,000
Deferred tax liabilities, net	3,120
Financial advisory and legal fees			578
Revenue, actual			3,000
Income (loss), actual			$ (4,000)
Sage Data Security, LLC
Business Acquisition [Line Items]
Payments to acquire business	11,600
Tangible assets acquired	1,800
Liabilities assumed	(730)
Goodwill	3,500
Identifiable intangible assets	$ 7,000
Weighted average useful life (in years)	14 years
Customer Relationships | Socrata, Inc.
Business Acquisition [Line Items]
Weighted average useful life (in years)	14 years