Acquisitions - Narrative (Details) - USD ($) $ in Thousands	May 01, 2018	Jan. 02, 2018	Jun. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, high			$ 19,581
Business acquisition, contingent consideration accounts payable			1,500	$ 2,700
Business acquisition, contingent consideration other long term liability			200	1,500
Goodwill			172,975	$ 144,835
IC Axon
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 30,493
Business combination, contingent consideration arrangements, range of outcomes, value, high	3,500		3,500
Goodwill	21,494
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	36,106
Hula Partners
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 10,000
Goodwill		8,527
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		10,000
CLS
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, high			2,179
McKinney Rogers
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, high			$ 8,000
Customer relationships | IC Axon
Business Acquisition [Line Items]
Intangible assets, other than goodwill	$ 10,365
Customer relationships | Hula Partners
Business Acquisition [Line Items]
Intangible assets, other than goodwill		$ 1,367