Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (130,041)	$ (117,812)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization of fixed assets	8,237	5,412
Loss on disposal of property and equipment	101
Stock-based compensation	16,773	13,148
Amortization of other liabilities	(713)	(399)
Amortization of deferred financing costs	40	33
Forgiveness of long-term debt		(1,000)
Amortization of premium on short-term investments	412	1,020
Amortization of intangible assets	150
Changes in assets and liabilities:
Accounts receivable, net	(2,930)	(2,833)
Inventory, net	(989)	(2,015)
Prepaid expenses and other current assets	1,702	(1,907)
Accounts payable	(973)	(1,144)
Accrued liabilities	5,453	4,284
Lease incentive obligation	(159)	(415)
Accrued interest		(106)
Net cash used in operating activities	(102,937)	(103,734)
Cash flows from investing activities:
Purchases of marketable securities	(151,456)	(197,997)
Maturities of marketable securities	142,813	109,826
Purchases of property and equipment	(12,166)	(14,019)
Net cash used in investing activities	(20,809)	(102,190)
Cash flows from financing activities:
Proceeds from exercise of common stock options	1,049	961
Proceeds from sale of common stock, net of issuance costs	144,247	174,140
Payments on capital lease obligations		(360)
Proceeds from mortgage payable		3,756
Payments on mortgage payable	(124)
Proceeds in connection with the Company's employee stock purchase plan	1,048	759
Net cash provided by financing activities	146,220	179,256
Effects of exchange rate on cash and cash equivalents	(164)	59
Net increase (decrease) in cash and cash equivalents	22,310	(26,609)
Cash and cash equivalents, beginning of period	41,135	58,131
Cash and cash equivalents, end of period	63,445	31,522
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment acquired but not paid	549	3,521
Unrealized gain on available-for-sale investments	410	211
Issuance of 341,507 and 21,826 shares of common stock to fund the Company's 401(k) matching contribution for 2015 and 2014, respectively	2,151	835
Interest paid	$ 157	$ 9