Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (21,013)	$ (21,761)	$ (8,819)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation, amortization and accretion	10,728	11,577	9,396
Stock-based compensation	5,673	6,021	5,483
Loss on disposal of property and equipment	18		9
Realized loss/(gain) from investments	8
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(42)	94	(958)
Inventory	(319)	1,581	(1,326)
Accounts receivable	(793)	1,701	1,308
Accounts payable	(24)	(635)	747
Accrued and other liabilities	2,985	(1,769)	1,767
Deferred revenue	(1,217)	895	616
Related party deferred revenue	(831)	446	(444)
Net cash (used in) provided by operating activities	(4,827)	(1,850)	7,779
Cash flows from investing activities:
Purchase of short-term investments	(32,577)	(48,451)	(1,001)
Redemption of short-term investments	51,410	4,802	1,001
Purchase of property and equipment	(1,452)	(2,815)	(13,534)
Purchased and capitalized intangible assets	(803)	(1,194)	(1,585)
Net cash (used in) provided by investing activities	16,578	(47,658)	(15,119)
Cash flows from financing activities:
Proceeds from debt			25,000
Payment of debt	(23,000)	(2,000)	(26,514)
Proceeds from exercise of common stock options	1,160	1,190	2,654
Net cash (used in) provided by financing activities	(21,840)	(810)	1,140
Net decrease in cash and cash equivalents	(10,089)	(50,318)	(6,200)
Cash and cash equivalents at beginning of period	21,765	72,083	78,283
Cash and cash equivalents at end of period	11,676	21,765	72,083
Supplemental disclosure of cash flow information:
Cash paid for interest	652	666	790
Cash paid for income taxes, net of refunds received	5	21	8
Noncash investing/operating activities:
Transfer of property and equipment to inventory	1,543	999	393
Transfer of inventory to property and equipment	3,373
Additions to property, equipment and intangible assets not paid at the end of the period	$ 853	$ 360	$ 1,755