Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 395,140	$ 80,304
Short-term investments		112,187
Accounts receivable	3,986	3,977
Restricted investment	10,695	10,695
Inventory	2,921
Other current assets	22,002	17,380
Total current assets	434,744	224,543
Restricted cash and investments	784	783
Property and equipment, net of accumulated depreciation of $28,426 and $24,594 as of September 30, 2016 and December 31, 2015, respectively	35,620	37,344
Intangible assets, net of accumulated amortization of $3,054 and $2,620 as of September 30, 2016 and December 31, 2015, respectively	8,111	6,642
Other non-current assets	8,051	4,470
Total assets	487,310	273,782
Current liabilities:
Accounts payable	20,684	20,234
Accrued expenses	29,539	29,053
Current portion of long-term debt	10,107	5,936
Current portion of notes payable		2,493
Deferred revenue	3,303	3,303
Other current liabilities	1,300	1,275
Total current liabilities	64,933	62,294
Long-term debt	8,491	14,969
Deferred rent and other	5,262	6,172
Total liabilities	78,686	83,435
Commitments and contingencies (Note 12)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 3,333,333 shares authorized; none issued and outstanding
Common stock, $0.0001 par value, 99,000,000 shares authorized; 54,351,725 and 45,629,529 issued and outstanding at September 30, 2016 and December 31, 2015, respectively	5	5
Additional paid-in capital	1,486,487	1,089,508
Accumulated other comprehensive loss		(111)
Accumulated deficit	(1,077,868)	(899,055)
Total stockholders’ equity	408,624	190,347
Total liabilities and stockholders’ equity	$ 487,310	$ 273,782