Earning Per Common Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	[1]	Sep. 30, 2015	[2]	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	[3]	Sep. 30, 2014	Jun. 30, 2014	[4]	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Common Share [Abstract]
Net (loss) income	$ 3,328		$ (57,422)		$ 5,362	$ 4,285	$ 6,029		$ 9,116	$ 6,862		$ 3,649	$ (44,445)	$ 25,656	$ 29,290
Weighted average shares													10,254,000	10,225,000	10,175,000
Denominator for basic earnings per common share													10,254,000	10,225,000	10,175,000
Employee stock options													0	6,000	11,000
Other stock compensation plans													0	101,000	74,000
Dilutive potential common shares													0	107,000	85,000
Denominator for diluted earnings per common share - adjusted weighted average shares and assumed conversions													10,254,000	10,332,000	10,260,000
Basic (loss) earnings per common share	$ 0.33		$ (5.60)		$ 0.52	$ 0.42	$ 0.59		$ 0.89	$ 0.67		$ 0.36	$ (4.33)	$ 2.51	$ 2.88
Diluted (loss) earnings per common share	0.32		(5.60)		0.52	0.41	0.58		0.88	0.67		0.35	(4.33)	2.48	2.85
Dividends paid per common share	$ 0.04		$ 0.04		$ 0.04	$ 0.04	$ 0.04		$ 0.03	$ 0.03		$ 0.03	$ 0.16	$ 0.13	$ 0.12
Antidilutive shares excluded from computation of earnings per share													75,000	0	0

[1] Fourth quarter 2015 includes $2,279 pre-tax gain on sale of Tucson, AZ concrete tie facility.

[2] Third quarter 2015 includes $80,337 ($63,887 net of tax) impairment of goodwill related to the IOS and Chemtec reporting units.

[3] Fourth quarter 2014 includes a $4,766 warranty charge related to UPRR warranty claim.

[4] Second quarter 2014 includes a $4,000 warranty charge related to UPRR warranty claim.