Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 40,679	$ 58,131
Marketable securities	204,472	224,625
Accounts receivable	1,581	1,376
Inventory, net	5,423	4,017
Prepaid expenses and other current assets	3,892	3,528
Total current assets	256,047	291,677
Property and Equipment, at cost:
Laboratory equipment	10,932	10,381
Assets under construction	2,946	1,552
Computer equipment and computer software	8,818	7,577
Leasehold improvements	5,965	5,937
Furniture and fixtures	933	939
Property and Equipment, gross	29,594	26,386
Less-Accumulated depreciation	(8,027)	(6,439)
Net property and equipment	21,567	19,947
Other long-term assets	1,200	1,200
Total assets	278,814	312,824
Current Liabilities:
Accounts payable	2,001	2,647
Accrued liabilities	11,652	13,960
Capital lease obligation, current portion	269	360
Lease incentive obligation, current portion	554	554
Total current liabilities	14,476	17,521
Long-term debt	1,000	1,000
Long-term accrued interest	112	106
Other long-term liabilities	3,541	3,599
Lease incentive obligation, less current portion	1,476	1,614
Total liabilities	20,605	23,840
Commitments and contingencies
Stockholders' Equity:
Common stock, $0.01 par value Authorized—200,000,000 shares Issued and outstanding—88,913,304 and 88,626,042 shares at March 31, 2015 and December 31, 2014	889	887
Additional paid-in capital	713,858	709,019
Accumulated other comprehensive income (loss)	70	(115)
Accumulated deficit	(456,608)	(420,807)
Total stockholders' equity	258,209	288,984
Total liabilities and stockholders’ equity	$ 278,814	$ 312,824