Acquisitions - Summary of Allocation of Purchase Consideration and Estimated Values of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands		9 Months Ended
	May 18, 2018	Sep. 30, 2018	May 01, 2018	Apr. 03, 2018	Dec. 31, 2017
Assets acquired
Goodwill		$ 53,132			$ 31,328
UMS
Assets acquired
Accounts receivable		3,834
Other assets		1,383
Property and equipment		27
Goodwill		20,201		$ 20,200
Total assets acquired		41,225
Liabilities assumed
Accounts payable and accrued expenses		3,981
Deferred revenue		5,210
Other liabilities		150
Net assets acquired		31,884
Consideration paid
Cash paid, net of cash acquired		31,884
Total		31,884
UMS | Trade Names
Assets acquired
Intangible assets other than goodwill		520
UMS | Acquired Technology
Assets acquired
Intangible assets other than goodwill		1,460
UMS | Customer Relationships
Assets acquired
Intangible assets other than goodwill		13,800
PlanetRisk, Inc.
Assets acquired
Accounts receivable		2,862
Property and equipment		488
Goodwill		1,205	$ 1,200
Total assets acquired		5,815
Liabilities assumed
Accounts payable and accrued expenses		694
Deferred revenue		2,810
Other liabilities		290
Net assets acquired		2,021
Consideration paid
Cash paid, net of cash acquired		2,021
Total		2,021
PlanetRisk, Inc. | Acquired Technology
Assets acquired
Intangible assets other than goodwill		160
PlanetRisk, Inc. | Customer Relationships
Assets acquired
Intangible assets other than goodwill		1,100
Respond B.V.
Assets acquired
Accounts receivable		86
Other assets		87
Property and equipment		19
Goodwill	$ 1,500	1,488
Total assets acquired		3,020
Liabilities assumed
Accounts payable and accrued expenses		208
Deferred revenue		220
Other liabilities		257
Net assets acquired		2,335
Consideration paid
Cash paid, net of cash acquired		1,952
Note payable	400	383
Total	$ 2,300	2,335
Respond B.V. | Trade Names
Assets acquired
Intangible assets other than goodwill		80
Respond B.V. | Acquired Technology
Assets acquired
Intangible assets other than goodwill		160
Respond B.V. | Customer Relationships
Assets acquired
Intangible assets other than goodwill		$ 1,100