Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (41,818)	$ (78,326)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	786	489
Gain on sale of assets, net	(201)	(879)
Amortization of debt issuance costs	326	0
Amortization of debt discount	4,265	0
Deferred rent	(28)	(114)
Amortization of premiums on investments	512	269
Non-cash share-based compensation expense	19,879	8,976
Change in operating assets and liabilities:
Accounts receivable	(13,497)	(779)
Other current assets	(750)	0
Accounts payable and accrued liabilities	(7,870)	(6,927)
Cease-use liability	(62)	(66)
Other liabilities	(28)	0
Net cash used in operating activities	(38,486)	(77,357)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of investments	(139,354)	(57,877)
Sales and maturities of investments	84,086	116,085
Proceeds from sales of property and equipment	18	0
Purchases of property and equipment	(1,800)	(1,362)
Net cash (used in) provided by investing activities	(57,050)	56,846
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of common stock	16,135	1,531
Net cash provided by financing activities	16,135	1,531
Net decrease in cash, cash equivalents and restricted cash	(79,401)	(18,980)
Cash, cash equivalents and restricted cash at beginning of the period	259,212	88,150
Cash, cash equivalents and restricted cash at end of the period	$ 179,811	$ 69,170