Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net loss	$ (27,383)	$ (9,588)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of purchased premium/discount	795	455
Depreciation of fixed assets	745	642
Non-cash interest expense	0	487
Compensation expenses associated with stock-based compensation plans	13,595	5,294
Changes in operating assets and liabilities:
Accounts receivable	(450)	991
Other current assets	2,956	(2,881)
Inventory	(7,201)	1,078
Accounts payable and accrued expenses	4,037	232
Deferred revenue	(1,224)	(1,492)
Other	(190)	35
Payment related to discounts and interest converted to principal	(6,450)	0
Net cash used in operating activities	(20,770)	(4,747)
Cash flows from investing activities:
Purchase of investments	(236,160)	(114,573)
Proceeds from sale and maturity of investments	208,982	2,000
Purchase of fixed assets	(1,325)	(420)
Net cash used in investing activities	(28,503)	(112,993)
Cash flows from financing activities:
Gross proceeds from common stock offering	229,770	85,100
Fees associated with common stock offering	(14,019)	(5,392)
Repayment of long-term obligations	(75,715)	(931)
Proceeds from the issuance of common stock under employee stock purchase plan and exercise of stock options	6,532	3,218
Net cash provided by financing activities	146,568	81,995
Net increase (decrease) in cash and cash equivalents	97,295	(35,745)
Cash and cash equivalents at beginning of the period	19,392	68,085
Cash and cash equivalents at end of the period	116,687	32,340
Supplemental disclosure of cash flow information:
Interest paid	$ 7,687	$ 7,878