Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
U.S. federal statutory income tax rate	35.00%	35.00%
Change in valuation allowance during the year	$ 1,440,000	$ 2,224,000
Unrecognized tax benefits	2,880,000	2,800,000
Unrecognized tax benefits that would impact effective tax rate	$ 160,000	160,000
Open Tax Year	1998
Federal [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards	$ 578,378,000
Operating loss carryforward, tax effected, benefit to be recognized in additional paid-in capital	2,652,000	$ 1,908,000
Federal [Member] | Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforward	$ 6,789,000
Federal [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2018
Federal [Member] | Latest Tax Year [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2036
State [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards	$ 30,946,000
State [Member] | Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforward	$ 6,003,000
State [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2031
State [Member] | Latest Tax Year [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2036