Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Noncash investing and financing activity
Capital projects incurred but not yet paid	$ 13,104	$ 10,708
Purchase of a productive asset through seller-financing	0	1,010
Shares issued for acquisition of business	0	4,303
Dividends declared not yet paid	$ 4,342	$ 3,967