Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Supplemental Cash Flow Information [Abstract]
Interest paid	$ 23,327	$ 20,356
Noncash investing and financing activity
Capital projects incurred but not yet paid	13,941	6,319
Investment merger (decreasing equity method investments and non-controlling interest)	0	8,360
Dividends declared not yet paid	4,663	4,501
Debt resulting from accounting standard adoption	36,953	0
Railcar assets resulting from accounting standard adoption	$ 25,643	$ 0