CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities:
Net income (loss)	$ (2,160)	$ (2,330)
Adjustment to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	874	713
Amortization of debt issuance costs	23	48
Amortization of premium on short-term investments	59
Revaluation of warrant liability		(54)
Stock-based compensation	1,370	334
Changes in operating assets and liabilities:
Accounts receivable	(3,630)	528
Inventory	(11,455)	(1,911)
Prepaid expenses and other assets	543	(241)
Deferred revenue	139	245
Deferred rent	925	(47)
Accounts payable	(50)	632
Accrued compensation and benefits	(3,406)	(1,340)
Accrued liabilities	147	1,262
Net cash provided by (used in) operating activities	(16,621)	(2,161)
Investing activities:
Purchases of investments	(17,293)
Proceeds from maturities of investments	7,861
Purchases of property and equipment	(1,220)	(464)
Net cash used in investing activities	(10,652)	(464)
Financing activities:
Payments on capital lease financing obligations	(280)	(281)
Payments on term loans	(159)	(11,775)
Proceeds from term loans		19,400
Proceeds from exercise of stock options and employee stock purchase plan	1,983	51
Payments of deferred offering costs	(600)	(69)
Net cash provided by (used in) financing activities	944	7,326
Net increase (decrease) in cash and cash equivalents	(26,329)	4,701
Cash and cash equivalents
Beginning of period	33,636	10,121
End of period	$ 7,307	$ 14,822