Description of Business and Summary of Significant Accounting Policies (Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs) (Details) - USD ($)		9 Months Ended		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation:
Beginning balance		$ 8,510,000	$ 4,277,000	$ 4,277,000
(Gains) or losses included in earnings	[1]	(164,000)		(1,344,000)
Goodwill, Translation and Purchase Accounting Adjustments	[1]	(3,432,000)	$ (664,000)	(664,000)
Foreign currency translation adjustments	[2]	153,000		(208,000)
Business acquisitions		34,112,000		6,449,000
Settlements		0		0
Ending balance		39,179,000		8,510,000
The amount of total (gains) losses for the period included in earnings or changes to net assets, attributable to changes in unrealized gains relating to assets or liabilities still held at period-end. Vertex earnout period expired in the third quarter of 2016 and gain was realized.		$ 0		$ (624,000)

[1] Recorded as an adjustment to reported general and administrative expenses

[2] Recorded as a component of other comprehensive income within stockholders' equity