Goodwill and Intangible Assets, Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets, Net [Abstract]
Gross carrying amounts	$ 90,038	$ 80,428
Accumulated amortization	(38,972)	(35,313)
Net carrying amount	51,066	45,115
Customer Relationships [Member]
Intangible Assets, Net [Abstract]
Gross carrying amounts	75,407	67,648
Accumulated amortization	(32,307)	(30,458)
Net carrying amount	43,100	37,190
Non-Compete Agreements [Member]
Intangible Assets, Net [Abstract]
Gross carrying amounts	1,556	1,018
Accumulated amortization	(707)	(557)
Net carrying amount	849	461
Customer Backlog [Member]
Intangible Assets, Net [Abstract]
Gross carrying amounts	1,650	390
Accumulated amortization	(866)	(195)
Net carrying amount	784	195
Trade Name [Member]
Intangible Assets, Net [Abstract]
Gross carrying amounts	100	30
Accumulated amortization	(53)	(7)
Net carrying amount	47	23
Internally Developed Software [Member]
Intangible Assets, Net [Abstract]
Gross carrying amounts	11,325	11,342
Accumulated amortization	(5,039)	(4,096)
Net carrying amount	$ 6,286	$ 7,246