Receivables (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 705,000	$ 677,000	$ 858,000
Provision for doubtful accounts	178,000	194,000	304,000
Additions related to acquired businesses	58,000	5,000	0
Recoveries	4,000	1,000	8,000
Accounts written off	(28,000)	(172,000)	(493,000)
Balance at end of period	917,000	705,000	677,000
Allowance for prompt payment discounts	$ 400,000	$ 300,000