Acquisitions - Narrative (Details) $ in Thousands				1 Months Ended
	Aug. 31, 2017 USD ($)	Apr. 01, 2017 USD ($)	Feb. 01, 2017 USD ($) period	Jul. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, range of outcomes, value, high					$ 25,099
Business acquisition, contingent consideration accounts payable					5,300	$ 3,600
Business acquisition, contingent consideration other long term liability					4,300	1,700
Goodwill					144,374	$ 127,772
CLS
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 400
Business combination, contingent consideration arrangements, range of outcomes, value, high	2,100				2,132
Total purchase price	1,300
Goodwill	1,000
McKinney Rogers
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross			$ 3,259
Business combination, contingent consideration arrangements, range of outcomes, value, high			$ 18,000		$ 12,967
Business combination, contingent consideration, term of earnings targets			5 months
Number of twelve-month earnings target Measurement Periods | period			3
Total purchase price			$ 7,764
Goodwill			5,196
Emantras
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 3,191
Business combination, contingent consideration arrangements, range of outcomes, value, high		300
Total purchase price		3,411
Goodwill		3,156
Target Earnings Measurement Period One | McKinney Rogers
Business Acquisition [Line Items]
Business combination, contingent consideration, amount contingent upon achievement of certain earnings targets			6,000
Contingent consideration paid				$ 1,000
Target Earnings Measurement Period Two | McKinney Rogers
Business Acquisition [Line Items]
Business combination, contingent consideration, amount contingent upon achievement of certain earnings targets			12,000
Customer relationships | CLS
Business Acquisition [Line Items]
Intangible assets, other than goodwill	$ 300
Customer relationships | McKinney Rogers
Business Acquisition [Line Items]
Intangible assets, other than goodwill			$ 653
Customer relationships | Emantras
Business Acquisition [Line Items]
Intangible assets, other than goodwill		$ 818