Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	$ 917	$ 705	$ 677
Provision for doubtful accounts	(5)	178	194
Additions related to acquired businesses	33	58	5
Recoveries	8	4	1
Accounts written off	(109)	(28)	(172)
Balance at end of period	844	917	$ 705
Allowance for prompt payment discounts	$ 400	$ 400