Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows from Operating Activities:
Net loss	$ (20,977)	$ (15,681)	$ (14,232)
Adjustments to reconcile net loss to net cash used in operating activities:
Discount accretion and other debt-related costs	436
Depreciation and amortization	5,946	4,942	3,128
Stock-based compensation	5,324	5,402	4,178
Provision for uncollectible amounts	287
Change in fair value of warrant liability	(167)	(3)	124
Changes in assets and liabilities:
Receivables	(3,932)	(1,403)	(1,076)
Prepaid expenses	71	(623)	(1,021)
Other current assets	(62)	(118)	192
Other long-term assets	(3,615)	1,028	936
Accounts payable	375	(29)	352
Accrued compensation and related costs	(459)	520	397
Unearned revenue	(2,307)	(2,416)	310
Other current liabilities	722	(1,675)	(73)
Other long-term liabilities	582	3,667	(149)
Total adjustments	3,201	9,292	7,298
Net cash used in operating activities	(17,776)	(6,389)	(6,934)
Cash Flows from Investing Activities:
Capital expenditures	(3,714)	(4,917)	(766)
Investment in intangible assets	(349)	(171)	(251)
Net cash used in investing activities	(4,063)	(5,088)	(1,017)
Cash Flows from Financing Activities:
Proceeds from term loan and other borrowings	28,880
Repayments of term loan and other borrowings	(6,945)	(750)
Proceeds from line of credit	16,246	15,000	7,000
Repayments of line of credit	(16,246)	(15,000)	(7,000)
Fees paid for issuance of term loan	(724)
Proceeds from issuance of common stock, net		15,942	11,138
Principal payments on capital lease obligations	(2,296)	(2,116)	(1,701)
Cash paid to satisfy tax withholding upon employee vesting	(440)	(874)	(797)
7% Series B convertible preferred stock dividend	(10)
Proceeds from exercise of stock options	236	241	13
Proceeds from employee stock purchase	289	212	152
Net cash provided by financing activities	18,990	12,655	8,805
Effect of exchange rate changes on cash and cash equivalents	(20)	(9)	(8)
(Decrease) increase in cash and cash equivalents	(2,869)	1,169	846
Cash and cash equivalents, beginning of period	15,407	14,238	13,392
Cash and cash equivalents, end of period	12,538	15,407	14,238
Non-Cash Investing and Financing Transactions:
Capital lease obligations incurred	2,447	2,737	1,692
Capital equipment purchased on credit	2,447	2,737	1,692
Financing of intellectual property purchased, at fair value		1,958
Issuance of warrant, at fair value	924		380
Supplemental Disclosures of Cash Flow Information:
Interest paid	$ 1,343	$ 314	$ 266