Business Acquisitions (Intangible Assets Acquired) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Total acquired intangible assets, Fair Value	$ 11,267	$ (3,184)
Acquired intangible assets, Weighted Average Useful Life (in years)	17 years 6 months 25 days	8 years 8 months 10 days
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Total acquired intangible assets, Fair Value	$ 518	$ 3,929
Acquired intangible assets, Weighted Average Useful Life (in years)	10 years	9 years 8 months 12 days
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Total acquired intangible assets, Fair Value	$ 0	$ 1,056
Acquired intangible assets, Weighted Average Useful Life (in years)	0 days	4 years 11 months 16 days
Trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Total acquired intangible assets, Fair Value	$ 10,499	$ 0
Acquired intangible assets, Weighted Average Useful Life (in years)	17 years 11 months 12 days	0 days
Final Allocation Adjustment [Member] | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Total acquired intangible assets, Fair Value	$ 250	$ (8,169)
Acquired intangible assets, Weighted Average Useful Life (in years)	0 days	0 days