Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Deferred tax valuation allowance has been recorded against these assets		100.00%
Federal corporate tax rate		35.00%
Remeasurement of deferred tax assets and liabilities, deferred tax expense		$ 27,300,000
Deferred tax assets [Abstract]
Net operating loss carryforwards		66,251,000	$ 126,244,000
Tax credit carryforwards		33,899,000	29,970,000
Equipment, furnishings and other		4,909,000	9,297,000
Total deferred tax assets		105,059,000	165,511,000
Deferred tax liabilities		0	(301,000)
Net deferred tax assets		105,059,000	165,210,000
Valuation allowance		(105,059,000)	(165,210,000)
Deferred tax assets, net of valuation allowance		0	0
Net change in valuation allowance		60,200,000	21,400,000
Federal statutory rate to net loss before income taxes [Abstract]
Federal benefit at statutory rate		(11,895,000)	(17,262,000)	$ (19,919,000)
State income taxes, net of Federal taxes		(2,073,000)	(3,086,000)	(3,556,000)
State credits		(506,000)	(1,031,000)	(1,324,000)
Warranty liabilities		(465,000)	(1,301,000)	(1,509,000)
Other permanent differences		11,000	40,000	16,000
Provision related to change in valuation allowance		(60,358,000)	21,601,000	20,142,000
Federal rate adjustment		27,314,000	0	0
NQ Options		47,000	0	0
Current year tax credit		(665,000)	(1,119,000)	(2,050,000)
NOL Adjustments		45,521,000	0	0
Termination/Cancellation of Equity Compensation Awards		2,983,000	2,274,000	5,960,000
Return to provision		84,000	(118,000)	2,238,000
Other, net		3,000	3,000	3,000
Provision for income taxes		800	800	800
Change in unrecognized tax benefits		0
Unrecognized tax benefits accrued interest or penalties		$ 0	$ 0	$ 0
Plan [Member]
Operating Loss Carryforwards [Line Items]
Federal corporate tax rate	21.00%
Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Expiration Date		Dec. 31, 2022
Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Expiration Date		Dec. 31, 2037
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		$ 373,700,000
Federal [Member] | Restricted [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		136,800,000
Federal [Member] | Unrestricted [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		236,900,000
Federal [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforward		16,600,000
State [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		236,300,000
State [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforward		$ 21,900,000