Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities
Net loss	$ (70,794,000)	$ (90,711,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	10,715,000	8,841,000
Stock-based compensation expense	7,293,000	13,125,000
Amortization of premiums and discounts on marketable securities		18,000
Gain on disposal of long-lived assets		(139,000)
Gain on equity investment	(182,000)
Changes in operating assets and liabilities:
Accounts receivable	(3,759,000)	(5,439,000)
Receivable from Roche	(1,216,000)	(2,076,000)
Inventory	(12,679,000)	1,655,000
Prepaid expenses and other current assets	4,165,000	195,000
Other assets	(627,000)	133,000
Accounts payable	3,631,000	4,430,000
Accrued expenses and other current liabilities	(8,752,000)	4,184,000
Deferred rent and other non-current liabilities	(736,000)	(126,000)
Deferred revenue	8,352,000	(178,000)
Roche related-party deferred revenue	4,370,000	(5,000)
Net cash used in operating activities	(60,219,000)	(66,093,000)
Investing activities
Purchases of property and equipment	(12,997,000)	(6,705,000)
Purchases of marketable securities and other investments		(4,996,000)
Proceeds from maturities of marketable securities		49,390,000
Net cash (used in) provided by investing activities	(12,997,000)	37,689,000
Financing activities
Proceeds from indebtedness to Roche	50,000,000
Proceeds from stock option exercises	5,316,000	2,188,000
Net cash provided by financing activities	55,316,000	2,188,000
Net decrease in cash, cash equivalents, and restricted cash	(17,900,000)	(26,216,000)
Effect of exchange rate changes on cash and cash equivalents	(86,000)	41,000
Cash, cash equivalents, and restricted cash at beginning of period	73,709,000	65,012,000
Cash, cash equivalents, and restricted cash at end of period	55,723,000	38,837,000
Supplemental disclosure of non-cash investing and financing activities
Cash paid for interest	2,212,000	150,000
Acquisition of property and equipment included in accounts payable and accrued expenses	$ 11,690,000	$ 1,247,000