Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Noncash or Part Noncash Acquisitions [Line Items]
Interest	$ 4,072	$ 4,338	$ 4,306
Income taxes	9,838	5,485	3,863
Total interest and income taxes paid	13,910	9,823	8,169
Series of Business Acquisitions | Common Stock
Noncash or Part Noncash Acquisitions [Line Items]
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Value of Shares Repurchased	91	0	0
Shares issued as payment of contingent consideration	4,678	2,012	1,570
Total shares issued for acquisition and contingent consideration	$ 4,769	$ 2,012	$ 1,570