Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Noncash investing and financing activity
Capital projects incurred but not yet paid	$ 7,305	$ 3,710
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	$ 4,341	$ 3,985