Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	$ 844	$ 917	$ 705
Provision for doubtful accounts	(83)	(5)	178
Additions related to acquired businesses	29	33	58
Recoveries	0	8	4
Accounts written off	(135)	(109)	(28)
Balance at end of period	655	844	$ 917
Allowance for prompt payment discounts	$ 500	$ 400