Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (50,688)	$ (267,265)	$ (220,030)
Adjustments to reconcile net loss to cash flows in operating activities:
Gain from sale of Priority Review Voucher	(125,000)
Depreciation and amortization	8,092	5,611	5,247
(Accretion of discount) amortization of premium on available-for-sale securities	(888)	80	652
Non-cash interest expense	2,679	355	367
Loss on disposal of assets	805	293	197
Stock-based compensation	30,465	29,962	32,117
Non-cash restructuring expense		911
Changes in operating assets and liabilities, net:
Increase in accounts receivable	(24,240)	(1,251)	(1,561)
Increase in inventory	(70,792)	(12,813)
(Increase) decrease in other assets	(15,354)	(9,012)	15,249
Increase in accounts payable, accrued expenses, deferred revenue and other liabilities	12,925	7,309	18,297
Net cash used in operations	(231,996)	(245,820)	(149,465)
Cash flows from investing activities:
Purchase of property and equipment	(12,000)	(5,341)	(3,401)
Purchase of intangible assets	(9,215)	(1,525)	(1,432)
Purchase of available-for-sale securities	(589,520)	(195,427)	(162,001)
Proceeds from sale of Priority Review Voucher	125,000
Purchase of restricted investment			(10,695)
Maturity of restricted investment	10,695
Maturity and sales of available-for-sale securities	296,225	112,100	185,939
Net cash (used in) provided by investing activities	(178,815)	(90,193)	8,410
Cash flows from financing activities:
Proceeds from term loan	30,000		20,000
Proceeds from revolving line of credit	39,708
Payments of term loan and notes payable	(15,109)	(7,603)	(2,598)
Payment of revolving line of credit	(39,645)
Proceeds from sales of common stock, net of offering costs	353,959	364,802	119,916
Proceeds from convertible debt offering	570,000
Debt issuance costs	(15,154)		(399)
Purchase of capped call options	(50,901)
Proceeds from exercise of options and warrants and employee stock purchase program	15,224	20,930	10,889
Net cash provided by financing activities	888,082	378,129	147,808
Increase in cash, cash equivalents and restricted cash	477,271	42,116	6,753
Cash, cash equivalents and restricted cash:
Beginning of period	122,556	80,440	73,687
End of period	599,827	122,556	80,440
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	1,912	1,562	769
Cash paid during the period for income taxes	5,336
Supplemental schedule of non-cash investing activities and financing activities:
Accrued exit and legal fees for debts	625	400	400
Reclassification of software licenses	204
Property and equipment reclassified to asset held for sale	1,529
Property and equipment included in accrued expenses	2,525	1,186	318
Intangible assets included in accrued expenses	343	1,163	335
Shares withheld for taxes	$ 2,227	2,168	$ 182
Accrual for offering costs related to the equity offerings		$ 53