Business Segments (Reconciliation of Operating Profit (Loss) from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting [Abstract]
Profit for reportable segments	$ 12,710	$ 8,558	$ 16,661	$ 10,367
Interest expense	(1,654)	(2,181)	(3,612)	(4,289)
Interest income	24	54	95	110
Other (expense) income	(128)	18	480	13
LIFO expense	(549)	(192)	(713)	(181)
Equity in income (loss) of nonconsolidated investments	0	145	(3)	(55)
Unallocated corporate expense and other unallocated charges	(4,790)	(2,903)	(8,792)	(4,457)
Income before income taxes	$ 5,613	$ 3,499	$ 4,116	$ 1,508