Business Combinations - Summary of Allocation of Purchase Consideration and Estimated Values of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands		9 Months Ended
	Jan. 27, 2017	Sep. 30, 2017	Dec. 31, 2016
Assets acquired
Goodwill		$ 31,343	$ 9,676
IDV Solutions LLC
Assets acquired
Accounts receivable		1,462
Other assets		242
Property and equipment		174
Goodwill	$ 21,200	21,196
Total assets acquired		30,794
Liabilities assumed
Accounts payable and accrued expenses		347
Deferred revenue		4,060
Other liabilities		132
Net assets acquired		26,255
Consideration paid
Cash paid, net of cash acquired		21,235
Acquisition date fair value of contingent consideration		5,020
Total	$ 5,000	26,255
IDV Solutions LLC | Trade Names
Assets acquired
Intangible assets other than goodwill		1,590
IDV Solutions LLC | Acquired Technology
Assets acquired
Intangible assets other than goodwill		2,490
IDV Solutions LLC | Customer Relationships
Assets acquired
Intangible assets other than goodwill		3,400
IDV Solutions LLC | Non-compete Arrangement
Assets acquired
Intangible assets other than goodwill		$ 240