Income Taxes (Reconciliation of the Federal Statutory and Effective Income Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income from continuing operations before income tax provision	$ 42,163	$ 29,102
Statutory taxes at 21.0% and 35.0%, respectively	8,854	10,186
State and local income taxes	1,241	493
Valuation allowances	640	(1,453)
Non-deductible expenses	663	224
Percentage depletion	(4,199)	(6,253)
R&D and other federal credits	(37)	301
Effect of the TCJA	0	(3,132)
Other, net	216	273
Income tax provision from continuing operations	$ 7,378	$ 639
Effective income tax rate from continuing operations	17.50%	2.20%