Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental disclosure of cash flow information
Interest paid	$ 21,407	$ 19,292	$ 19,944
Income taxes paid, net of refunds	(10,587)	4,909	36,783
Noncash investing and financing activity
Capital projects incurred but not yet paid	3,092	7,507	6,000
Purchase of a productive asset through seller-financing	0	1,010	6,634
Shares issued for acquisition of business	0	4,303	31,050
Outstanding shares to be issued for acquisition of business	0	0	4,470
Dividends declared not yet paid	$ 4,493	$ 4,338	$ 4,059