Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
CASH FLOWS USED IN OPERATING ACTIVITIES:
Net loss	$ (130,437)	$ (125,377)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,341	695
Amortization of discount on marketable securities, net	(278)	(75)
Amortization of debt discount and debt issuance costs	6,668	0
Stock-based compensation	15,569	20,533
Changes in operating assets and liabilities:
Inventory	(1,854)	(1,636)
Accounts receivable, net	(6,516)	(1,211)
Prepaid expenses	(1,352)	(3,738)
Other current assets	724	113
Other long-term assets	166	(7)
Accounts payable	(1,383)	(1,732)
Accrued expenses and other current liabilities	(4,221)	(466)
Other non-current liabilities	(47)	(48)
Net cash used in operating activities	(121,620)	(112,949)
CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES:
Purchases of property and equipment	(71)	(1,131)
Payments for capitalized milestones	0	(8,712)
Purchases of marketable securities	(499)	(111,983)
Sales and maturities of marketable securities	45,000	106,264
Net cash provided by (used in) investing activities	44,430	(15,562)
CASH FLOWS PROVIDED BY FINANCING ACTIVITIES:
Proceeds from exercise of stock options and warrant exercises	8,826	4,024
Proceeds from issuance of shares under employee stock purchase plan	1,741	1,030
Net cash provided by financing activities	10,567	5,054
NET DECREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(66,623)	(123,457)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT BEGINNING OF YEAR	118,619	258,614
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT END OF PERIOD	51,996	135,157
SUPPLEMENTAL DISCLOSURES:
Cash paid for income taxes	22	21
Property and equipment purchases in accrued expenses at period end	$ 114	$ 1,247