Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash paid during the period for:
Income taxes, net	$ 89	$ 482
Interest, net	1,343	678
Non-Cash Financing and Investing Transactions:
Employee stock purchase plan	132	127
Shares tendered in payment of exercise price of stock options	46	0
Equipment acquired under capital leases	$ 0	$ 441