Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (361,918)	$ (50,688)	$ (267,265)
Adjustments to reconcile net loss to cash flows in operating activities:
Gain from sale of Priority Review Voucher		(125,000)
Depreciation and amortization	12,245	8,092	5,611
Amortization of investment (discount) premium	(7,672)	(888)	80
Loss from extinguishment of debt	2,322
Non-cash interest expense	20,190	2,679	355
Loss on disposal of assets	3,938	805	293
Stock-based compensation	50,127	30,465	29,962
Non-cash restructuring expense			911
Changes in operating assets and liabilities, net:
Net increase in accounts receivable	(19,576)	(24,240)	(1,251)
Net increase in inventory	(41,840)	(70,792)	(12,813)
Net increase in other assets	(136,638)	(15,354)	(9,012)
Net increase in accounts payable, accrued expenses, deferred revenue and other liabilities	90,162	12,925	7,309
Net cash used in operations	(388,660)	(231,996)	(245,820)
Cash flows from investing activities:
Purchase of property and equipment	(61,157)	(12,000)	(5,341)
Purchase of intangible assets	(3,188)	(9,215)	(1,525)
Purchase of available-for-sale securities	(1,171,603)	(589,520)	(195,427)
Maturity and sales of available-for-sale securities	865,813	296,225	112,100
Proceeds from sale of Priority Review Voucher		125,000
Purchase of restricted investment	(353)
Maturity of restricted investment		10,695
Net cash used in investing activities	(370,488)	(178,815)	(90,193)
Cash flows from financing activities:
Proceeds from July 2017 Term Loan		30,000
Repayment of June 2015 and July 2017 Term Loan	(30,000)	(15,000)	(5,000)
Repayment of mortgage loans and notes payable	(1,265)	(109)	(2,603)
Proceeds from revolving line of credit	235,872	39,708
Repayment of revolving line of credit	(235,954)	(39,645)
Payment for debt extinguishment	(2,134)
Proceeds from sales of common stock, net of offering costs	513,409	353,959	364,802
Proceeds from convertible debt offering		570,000
Debt issuance costs		(15,154)
Purchase of capped call options		(50,901)
Proceeds from exercise of options and employee stock purchase program	50,222	15,224	20,930
Net cash provided by financing activities	530,150	888,082	378,129
(Decrease) increase in cash and cash equivalents	(228,998)	477,271	42,116
Cash, cash equivalents and restricted cash:
Beginning of period	599,827	122,556	80,440
End of period	370,829	599,827	122,556
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	$ 370,829	599,691	122,420
Restricted cash in other assets		$ 136	$ 136
Restricted Cash, Noncurrent, Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Total cash, cash equivalents and restricted cash	$ 370,829	$ 599,827	$ 122,556
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	11,308	1,912	1,562
Cash paid during the period for income taxes	1,548	5,336
Supplemental schedule of non-cash investing activities and financing activities:
Accrued exit and legal fees for debts		625	400
Reclassification of software licenses		204
Property and equipment reclassified to asset held for sale		1,529
Property and equipment included in accrued expenses	5,421	2,525	1,186
Intangible assets included in accrued expenses	374	343	1,163
Shares withheld for taxes	9,061	$ 2,227	$ 2,168
Reclassification of long term investments to short term investments	$ 9,980