Income Taxes (Provision for Income Taxes from Continuing Operations Differs from the Federal Statutory Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Statutory rate	$ 27,268	$ 17,494	$ 12,985
State taxes, less federal effect	2,442	3,033	1,845
Tax effect of Tax Reform Act	(12,535)	0	0
Domestic manufacturer's deduction	(1,578)	(1,363)	(795)
Excess tax benefit on stock based compensation	(1,415)	0	0
Federal tax credits	(373)	(439)	(242)
Uncertain tax positions	(148)	(154)	(344)
Change in valuation allowance	660	685	284
Non-deductible expenses	499	556	2
Foreign rate differential	2	(677)	(6)
Intangible asset impairment	0	341	0
Worthless stock deduction	0	(868)	0
Intercompany debt discharge	0	(2,389)	0
Other	121	45	(105)
Provision for income taxes	$ 14,943	$ 16,264	$ 13,624
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory rate	35.00%	35.00%	35.00%
State taxes, less federal effect	3.10%	6.10%	5.00%
Tax effect of Tax Reform Act	(16.10%)	0.00%	0.00%
Domestic manufacturer's deduction	(2.00%)	(2.70%)	(2.10%)
Excess tax benefit on stock based compensation	(1.80%)	(0.00%)	(0.00%)
Federal tax credits	(0.50%)	(0.90%)	(0.70%)
Uncertain tax positions	(0.20%)	(0.30%)	(0.90%)
Change in valuation allowance	0.80%	1.40%	0.70%
Non-deductible expenses	0.70%	1.10%	0.00%
Foreign rate differential	0.00%	(1.40%)	0.00%
Intangible asset impairment	0.00%	0.70%	0.00%
Worthless stock deduction	(0.00%)	(1.70%)	(0.00%)
Intercompany debt discharge	(0.00%)	(4.80%)	(0.00%)
Other	0.20%	0.00%	(0.30%)
Effective income tax rate, percentage	19.20%	32.50%	36.70%