CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net loss	$ (65,087)	$ (65,319)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	900	1,083
Share-based compensation	13,998	10,269
Other	(890)	53
Changes in operating assets and liabilities:
Accounts receivable	280	(587)
Receivables from collaborative arrangements	4,264	1,437
Other prepaid and current assets	(1,578)	(1,237)
Inventories	(371)	140
Tax receivable	5,092
Other assets		266
Accounts payable	(449)	2,004
Accrued personnel-related expenses, accrued clinical and development expenses, and other accrued liabilities	(5,076)	(3,214)
Deferred rent	2,104	(292)
Deferred revenue	95,371	17
Other long-term liabilities	1,267	5,354
Net cash provided by (used in) operating activities	49,825	(50,026)
Investing activities
Purchases of property and equipment	(2,771)	(587)
Purchases of marketable securities	(54,839)	(159,217)
Maturities of marketable securities	46,299	36,282
Proceeds from the sales of fixed assets	17
Net cash (used in) investing activities	(11,294)	(123,522)
Financing activities
Proceeds from option exercises	35	2,816
Repurchase of shares to satisfy tax withholding	(1,715)	(4,032)
Net cash (used in) financing activities	(1,680)	(1,216)
Net increase (decrease) in cash, cash equivalents, and restricted cash	36,851	(174,764)
Cash, cash equivalents, and restricted cash at beginning of period	89,813	345,542
Cash, cash equivalents, and restricted cash at end of period	126,664	$ 170,778
Supplemental disclosure of cash flow information
Cash received for income taxes, net	$ 4,473