Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (153,237)	$ (160,108)	$ (80,612)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	3,067	2,427	806
Share-based compensation	26,764	24,929	10,414
Deferred income taxes	(2,200)	(3,248)	(963)
Interest expense under build-to-suit lease transaction	3,688	863	0
Gain from early lease retirement	(2,096)	0	0
(Gain) loss on disposal of fixed asset	(5)	0	20
Loss on sublease	0	0	261
Changes in operating assets and liabilities:
Receivable from Roche	(62)	331	1,220
Receivable from related party	0	0	30
Prepaid and other assets	7,249	(3,363)	937
Accounts payable, accruals and other liabilities	147	15,193	11,161
Net cash used in operating activities	(131,183)	(116,250)	(58,600)
Investing activities
Purchases of property and equipment	(3,626)	(16,644)	(1,382)
Proceeds from disposal of fixed asset	105	0	0
Net cash used in investing activities	(3,521)	(16,644)	(1,382)
Financing activities
Proceeds from issuance of ordinary shares in public offering, net	150,323	128,777	131,341
Proceeds from issuance of ordinary shares upon exercise of stock options	17,838	10,516	5,648
Proceeds from tenant improvement allowance under build-to-suit lease	0	14,163	0
Reduction of build-to-suit lease obligation	(2,760)	(169)	0
Net cash provided by financing activities	165,401	153,287	136,989
Net increase in cash, cash equivalents and restricted cash	30,697	20,393	77,007
Cash, cash equivalents and restricted cash, beginning of the year	390,979	370,586	293,579
Cash, cash equivalents and restricted cash, end of the period	421,676	390,979	370,586
Supplemental disclosures of cash flow information
Cash paid for income taxes, net of refunds	294	575	442
Supplemental disclosures of non-cash investing and financing activities
Acquisition of property and equipment included in accounts payable and accrued liabilities	175	575	185
Amounts capitalized under build-to-suit lease transaction	0	36,805	0
Interest capitalized during construction period for build-to-suit lease transaction	0	1,179	0
Stock option shortfall	0	(258)	0
Offering costs included in accounts payable and accrued liabilities	$ 0	$ 0	$ 18