Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss		$ (178,813)	$ (155,349)
Adjustments to reconcile net loss to cash flows from operating activities:
Depreciation and amortization		3,947	3,883
Amortization of premium on available-for-sale securities, loss from sale of available-for-sale securities and non-cash interest		473	805
Loss on abandonment of patents		45	180
Stock-based compensation		23,093	25,769
Non-cash restructuring expenses	[1]	504
Changes in operating assets and liabilities, net:
Net increase in accounts receivable		(9)	(317)
Net increase in inventory		(2,921)
Net (increase) decrease in other assets		(8,203)	9,963
Net decrease in accounts payable, accrued expenses, deferred revenue and other liabilities		(2,703)	(3,127)
Net cash used in operating activities		(164,587)	(118,193)
Cash flows from investing activities:
Purchase of property and equipment		(2,427)	(2,316)
Purchase of intangible assets		(1,093)	(982)
Purchase of restricted investments			(10,695)
Purchase of available-for-sale securities			(49,632)
Sale and maturity of available-for-sale securities		112,101	141,854
Net cash provided by investing activities		108,581	78,229
Cash flows from financing activities:
Proceeds from borrowings, net of debt issuance costs			19,601
Repayments of long-term debt and notes payable		(5,076)	(2,573)
Proceeds from sales of common stock		364,951
Proceeds from exercise of options and purchase of stock under the Employee Stock Purchase Program		10,967	5,204
Net cash provided by financing activities		370,842	22,232
Increase (decrease) in cash and cash equivalents		314,836	(17,732)
Cash and cash equivalents:
Beginning of period		80,304	73,551
End of period		395,140	55,819
Supplemental disclosure of cash flow information:
Cash paid during the period for interest		1,199	359
Supplemental schedule of non-cash investing activities and financing activities:
Shares withheld for taxes		1,955
Accrual for debt issuance costs related to the senior secured term loan		400	400
Intangible assets included in accrued expenses		1,230	105
Accrual for offering costs related to the equity offerings		$ 222	135
Property and equipment included in accrued expenses			211
Capitalized interest			$ 99

[1] The non-cash restructuring expense relates to acceleration of stock option vesting and accelerated depreciation for certain assets.