Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net loss	$ (47,473)	$ (35,801)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization of fixed assets	2,473	1,587
Stock-based compensation	6,100	3,620
Amortization of other liabilities	(208)	(58)
Amortization of deferred financing costs	13
Amortization of premium on short-term investments	214	377
Amortization of intangible assets	50
Changes in assets and liabilities:
Accounts receivable, net	(688)	(205)
Inventory, net	(1,480)	(1,406)
Prepaid expenses and other current assets	(347)	(364)
Accounts payable	(467)	(646)
Accrued liabilities	(664)	(2,309)
Lease incentive obligation	130	(138)
Accrued interest		6
Net cash used in operating activities	(42,347)	(35,337)
Cash flows from investing activities:
Purchases of marketable securities	(6,118)	(11,145)
Maturities of marketable securities	61,680	31,116
Purchases of property and equipment	(2,389)	(2,371)
Net cash used in investing activities	53,173	17,600
Cash flows from financing activities:
Proceeds from exercise of common stock options	288	386
Payments on capital lease obligations		(91)
Payments on mortgage payable	(41)
Net cash provided by financing activities	247	295
Effects of exchange rate on cash and cash equivalents	(57)	(10)
Net increase (decrease) in cash and cash equivalents	11,016	(17,452)
Cash and cash equivalents, beginning of period	41,135	58,131
Cash and cash equivalents, end of period	52,151	40,679
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment acquired but not paid	1,034	836
Unrealized gain on available-for-sale investments	473	195
Issuance of 340,950 and 21,826 shares of common stock to fund the Company’s 401(k) matching contribution for 2015 and 2014, respectively	2,146	835
Interest paid	$ 53	$ 4