Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating activities
Net loss	$ (50,015)	$ (25,945)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	4,569	4,003
Stock-based compensation expense	3,789	1,856
Provision for doubtful accounts on accounts receivable	171
Provisions on inventory	105
Non-cash interest expense		11
Changes in operating assets and liabilities:
Accounts receivable	(264)	194
Receivable from Roche	(4,149)
Inventory	(1,438)	(830)
Prepaid expenses and other current assets	(2,810)	(156)
Other assets	(474)	(192)
Accounts payable	(1,452)	(2,077)
Accrued expenses and other current liabilities	1,761	(618)
Deferred rent and other non-current liabilities	2,257	(107)
Deferred revenue	(213)	204
Net cash used in operating activities	(48,163)	(23,657)
Investing activities
Purchases of property and equipment	(9,393)	(2,969)
Increase in restricted cash	(531)
Net cash used in investing activities	(9,924)	(2,969)
Financing activities
Proceeds from issuance of common stock to Roche, net of issuance costs	245,387
Proceeds from issuance of restricted stock and stock option exercises	4,216	229
Payments of notes payable		(842)
Net cash provided by (used in) financing activities	249,603	(613)
Net increase (decrease) in cash and cash equivalents	191,516	(27,239)
Cash and cash equivalents at beginning of period	72,080	124,293
Cash and cash equivalents at end of period	263,596	97,054
Supplemental disclosure of cash flow information
Cash paid for interest		123
Supplemental disclosure of non-cash investing and financing activities
Acquisition of property and equipment included in accounts payable and accrued expenses	$ 6,466	$ 627