Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net loss	$ (34,946)	$ (47,473)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization of fixed assets	3,247	2,473
Loss on disposal of property and equipment	20
Stock-based compensation	6,129	6,100
Amortization of other liabilities	(377)	(208)
Amortization of deferred financing costs	14	13
Amortization of premium on short-term investments	37	214
Amortization of intangible assets	50	50
Changes in assets and liabilities:
Accounts receivable, net	(7,688)	(688)
Inventory, net	(1,026)	(1,480)
Prepaid expenses and other current assets	(329)	(347)
Accounts payable	181	(467)
Accrued liabilities	1,204	(664)
Lease incentive obligation	(154)	130
Net cash used in operating activities	(33,638)	(42,347)
Cash flows from investing activities:
Purchases of marketable securities	(30,563)	(6,118)
Maturities of marketable securities	57,236	61,680
Purchases of property and equipment	(2,745)	(2,389)
Net cash provided by investing activities	23,928	53,173
Cash flows from financing activities:
Proceeds from exercise of common stock options	47	288
Payments on mortgage payable	(44)	(41)
Net cash provided by financing activities	3	247
Effects of exchange rate on cash and cash equivalents	(8)	(57)
Net increase (decrease) in cash and cash equivalents	(9,715)	11,016
Cash and cash equivalents, beginning of period	48,921	41,135
Cash and cash equivalents, end of period	39,206	52,151
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment acquired but not paid	775	1,034
Unrealized gain (loss) on available-for-sale investments	(5)	473
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	2,146
Interest paid	$ 50	$ 53