Acquired Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Assets eligible for amortization:
Gross Carrying Amount		$ 18,222	$ 16,817
Accumulated Amortization		(3,657)	(3,230)
Unamortized intangible assets:
Goodwill, Gross Carrying Amount	[1]	12,796	11,817
Goodwill, Accumulated Amortization	[1]	(227)	(227)
Customer Lists [Member]
Assets eligible for amortization:
Gross Carrying Amount		4,288	3,933
Accumulated Amortization		(2,702)	(2,342)
Patents [Member]
Assets eligible for amortization:
Gross Carrying Amount		72	72
Accumulated Amortization		(12)	(8)
Noncompete Agreements [Member]
Assets eligible for amortization:
Gross Carrying Amount		332	261
Accumulated Amortization		(291)	(261)
Software [Member]
Assets eligible for amortization:
Gross Carrying Amount		234	234
Accumulated Amortization		(234)	(234)
Other Intangible Assets [Member]
Assets eligible for amortization:
Gross Carrying Amount		500	500
Accumulated Amortization		$ (191)	$ (158)

[1] Amortization through December 31, 2001 prior to adoption of FASB ASC 350.