Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net loss	$ (65,736)	$ (92,238)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization of fixed assets	6,756	5,289
Loss on disposal of property and equipment	91	44
Stock-based compensation	12,224	10,607
Amortization of other liabilities	(769)	(445)
Amortization of deferred financing costs	26	26
Amortization of premium on short-term investments	57	346
Amortization of intangible assets	290	100
Changes in assets and liabilities:
Accounts receivable, net	(14,065)	(2,508)
Inventory, net	(5,577)	(1,727)
Prepaid expenses and other current assets	242	80
Accounts payable	1,527	(173)
Accrued liabilities	(268)	2,651
Lease incentive obligation	(308)	(23)
Net cash used in operating activities	(65,510)	(77,971)
Cash flows from investing activities:
Purchases of marketable securities	(188,248)	(6,118)
Maturities of marketable securities	146,475	97,004
Purchases of property and equipment	(8,648)	(6,415)
Purchases of intangible assets	(8,442)
Net cash (used in) provided by investing activities	(58,863)	84,471
Cash flows from financing activities:
Proceeds from exercise of common stock options	772	549
Proceeds from sale of common stock, net of issuance costs	253,463
Payments on mortgage payable	(86)	(82)
Proceeds in connection with the Company's employee stock purchase plan	1,629	1,047
Net cash provided by financing activities	255,778	1,514
Effects of exchange rate on cash and cash equivalents	81	(139)
Net increase in cash and cash equivalents	131,486	7,875
Cash and cash equivalents, beginning of period	48,921	41,135
Cash and cash equivalents, end of period	180,407	49,010
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment acquired but not paid	2,105	1,055
Unrealized gain (loss) on available-for-sale investments	(42)	555
Issuance of 158,717 and 341,507 shares of common stock to fund the Company's 401(k) matching contribution for 2016 and 2015, respectively	3,008	2,151
Interest paid	$ 101	$ 105