Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 38,196	$ 42,689
Marketable securities	135,383	164,619
Accounts receivable, net	4,265	4,598
Unbilled revenues	1,353	3,002
Inventories	15,096	15,334
Prepaid expenses and other current assets	3,799	3,685
Total current assets	198,092	233,927
Property, plant and equipment, net	34,311	36,080
Investment in unconsolidated joint venture	39,769	40,934
Other assets	1,423	1,648
Total assets	273,595	312,589
Current liabilities:
Accounts payable	5,938	8,319
Accrued liabilities	11,759	14,079
Current portion of long-term debt	0	6
Deferred revenue	900	1,050
Total current liabilities	18,597	23,454
Deferred revenue	0	150
Convertible debt, inclusive of derivative liabilities of $98 and $83 at March 31, 2015 and December 31, 2014, respectively; and net of unamortized debt discounts of $10,545 and $11,124 at March 31, 2015 and December 31, 2014, respectively.	200,686	200,091
Other liabilities	4,025	2,518
Total liabilities	223,308	226,213
Commitments and contingencies
Stockholders' equity:
Preferred stock, par value $0.001—5,000,000 shares authorized; 0 shares issued and outstanding	0	0
Common stock, par value $0.001—150,000,000 shares authorized; 80,055,550 and 79,388,069 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	80	79
Additional paid-in capital	570,366	565,769
Accumulated other comprehensive loss	(17,036)	(11,014)
Accumulated deficit	(503,123)	(468,458)
Total stockholders’ equity	50,287	86,376
Total liabilities and stockholders’ equity	$ 273,595	$ 312,589