Supplemental Cash Flow Information - Details of Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash paid during the year for:
Income taxes	$ 13,442	$ 24,330	$ 21,324
Interest, net	3,814	3,518	2,101
Non-Cash Financing and Investing Transactions:
Unsettled repurchases of common stock	556	898	935
Employee stock purchase plan	549	522	669
Equipment acquired under capital leases	0	937	1,153
Receivable for sale of Global's assets	0	1,979	0
Shares tendered in payment of exercise price of stock options	0	$ 0	$ 63
Proceeds from income tax refunds	$ 6,800