Business Acquisitions and Divestitures - Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Feb. 23, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 17,648		$ 13,823		$ 11,810
C&CA
Business Acquisition [Line Items]
Account receivables		$ 1,621
Commissions receivable		48
Prepaid expenses		109
Other current assets, net		6
Intangible Assets		10,923
Goodwill		3,554
Fixed Assets		323
Accounts payable		(125)
Accrued commissions		(537)
Total consideration paid		15,922
Contingent consideration		(5,954)
Total cash paid		$ 9,968
Lavante
Business Acquisition [Line Items]
Cash and cash equivalents				$ 28
Account receivables				207
Other current assets, net				92
Intangible Assets				6,178
Goodwill				2,286
Fixed Assets				98
Accounts payable				(121)
Deferred revenue				(370)
Other current liabilities				(757)
Total consideration paid				7,641
Contingent consideration				(3,832)
Total cash paid				$ 3,809