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Income Taxes (Income Tax Reconciliation) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory rate	34.00%	34.00%	34.00%
State and local taxes	1.50%	1.60%	1.50%
Domestic production credit	(14.30%)	(5.40%)	(3.60%)
Permanent stock differences	(13.40%)
Permanent stock differences		0.30%	1.10%
Other	(1.50%)	(6.90%)	0.50%
Effective rate prior to tax act	6.30%	23.60%	33.50%
Deferred re-measurement for rate change	(1144.40%)	0.00%	0.00%
Effective rate	(1138.10%)	23.60%	33.50%

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Effective Income Tax Rate, Prior to Tax Cut and Jobs Act of 2017, Continuing Operations

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Percentage of increase (decrease) in effective tax rate for measurement period adjustment from accounting for tax effect pursuant to Tax Cuts and Jobs Act of 2017.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to nondeductible expenses.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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