Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities
Net loss	$ (90,711)	$ (46,301)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	8,841	7,236
Stock-based compensation expense	13,125	7,670
Amortization of premiums and discounts on marketable securities	18	148
Gain on disposal of long-lived assets	(139)
Changes in operating assets and liabilities:
Accounts receivable	(5,439)	(3,056)
Receivable from Roche	(2,076)	(1,627)
Inventory	1,655	(2,168)
Prepaid expenses and other current assets	195	2,688
Other assets	(778)	18
Accounts payable	4,431	4,797
Accrued expenses and other current liabilities	4,184	2,323
Deferred rent and other non-current liabilities	(126)	(991)
Deferred revenue	(178)	467
Roche related-party deferred revenue	(5)
Net cash used in operating activities	(67,003)	(28,796)
Investing activities
Purchases of property and equipment	(6,705)	(11,996)
Purchases of marketable securities and other investments	(4,996)	(77,445)
Proceeds from maturities of marketable securities	49,390	62,453
Net cash provided by (used in) investing activities	37,689	(26,988)
Financing activities
Proceeds from stock option exercises	2,188	303
Net cash provided by financing activities	2,188	303
Net decrease in cash and cash equivalents	(27,126)	(55,481)
Effect of exchange rate changes on cash and cash equivalents	41
Cash and cash equivalents at beginning of period	63,617	117,763
Cash and cash equivalents at end of period	36,532	62,282
Supplemental disclosure of non-cash investing and financing activities
Cash paid for interest	150
Acquisition of property and equipment included in accounts payable and accrued expenses	$ 1,247	$ 1,941