Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Operating Activities
Net loss	$ (29,573)	$ (20,327)
Adjustments to reconcile net loss to net cash and cash equivalents used in operating activities:
Depreciation and amortization	936	1,064
Amortization of debt issuance costs	56	78
Remeasurement of fair value of preferred stock warrant liability		1,800
Stock-based compensation	2,018	484
Accretion of bond discount		(1)
Loss on disposal of property and equipment	5	32
Impairment loss on property and equipment		304
Changes in operating assets and liabilities:
Accounts receivable	150	251
Interest receivable	68	6
Inventory	434	667
Other current and long term assets	(240)	(527)
Restricted cash	125
Accounts payable	1,461	1,617
Accrued expenses	350	505
Net cash and cash equivalents used in operating activities	(24,210)	(14,047)
Investing Activities
Purchase of investments		(1,104)
Proceeds from sale and maturities of investments	6,191	907
Proceeds from sale of property and equipment	25
Cash received in acquisition of a business, net of cash paid		305
Purchase of property and equipment	(1,626)	(724)
Net cash and cash equivalents provided by (used in) investing activities	4,590	(616)
Financing Activities
Payment of debt	(2,877)	(601)
Proceeds from the issuance of common stock, net of issuance costs	52,433
Proceeds from issuance of debt, net of debt discount	4,321	1,998
Proceeds from issuance of preferred stock, net of issuance costs		28,199
Proceeds from exercise of stock options and warrants	73
Net cash and cash equivalents provided by financing activities	53,950	29,596
Net increase in cash and cash equivalents	34,330	14,933
Cash and Cash Equivalents, beginning of period	10,014	8,896
Cash and Cash Equivalents, end of period	44,344	23,829
Supplemental Disclosure for Cash Flow Information
Interest paid	518	625
Supplemental Schedule of Noncash Investing and Financing Activities
Issuance of preferred stock warrants and debt issuance costs		128
Issuance of common stock warrants	54
Conversion of bridge notes to preferred stock		1,998
Conversion of preferred stock warrants to common stock warrants		$ 1,909