Goodwill and Intangible Assets (Intangible Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 245,137	$ 214,810
Accumulated Amortization	68,093	59,270
Total intangible Assets, Gross Carrying Amount	249,711	219,548
Net Carrying Amount	177,044	155,540
Indefinite-lived other intangible asset	4,574	4,738
Total intangible assets, Net Carrying Amount	181,618	160,278
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	149,933	128,907
Accumulated Amortization	27,985	22,514
Net Carrying Amount	121,948	106,393
Technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	81,840	73,891
Accumulated Amortization	36,974	33,491
Net Carrying Amount	44,866	40,400
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	12,024	10,213
Accumulated Amortization	2,934	2,157
Net Carrying Amount	9,090	8,056
Covenants not to compete
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,340	1,799
Accumulated Amortization	200	1,108
Net Carrying Amount	$ 1,140	$ 691