Debt - Additional Information (Detail) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2011 Installment	Dec. 31, 2011 Installment	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2012 Installment	May 31, 2013	Feb. 28, 2013 Installment
Line of Credit Facility [Line Items]
Interest expense related to preferred stock warrants and common stock warrants issued		$ 251,000	$ 159,000
Revolving credit facility, amount outstanding	3,239,000	6,369,000					3,239,000
Letter of credit drawn current	0						0
Change in the valuation of outstanding preferred stock warrants	0	238,000	362,000
Equipment Advance Facilities [Member]
Line of Credit Facility [Line Items]
Increase in the revolving credit facility				2,000,000
Revolving credit facility, amended annual interest rate				5.50%
Frequency of payments, description	Repayable in 36 consecutive monthly installments of principal and interest
Number of monthly installments				36
Revolving credit facility, the expiration date				Dec. 01, 2014
Revolving credit facility, amount outstanding	1,697,000	3,771,000					1,697,000
Additional Equipment Advance Facility [Member]
Line of Credit Facility [Line Items]
Increase in the revolving credit facility					2,000,000
Revolving credit facility, amended annual interest rate					5.50%
Frequency of payments, description	Repayable in 36 consecutive monthly installments of principal and interest.
Number of monthly installments					36
Revolving credit facility, the expiration date					Sep. 01, 2015
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Increase in the revolving credit facility						15,000,000
Revolving credit facility, amended annual interest rate						0.25%
Revolving credit facility, the expiration date						Jul. 31, 2015
Percentage of eligible accounts receivable						80.00%
Unrestricted cash balance exceeds						50,000,000
Revolving credit facility, amount outstanding	0	0					0
Revolving credit facility, Description	In September 2013, the Company entered into an amendment to the Revolving Credit Facility pursuant to which Silicon Valley Bank agreed to increase the Revolving Credit Facility to the lesser of $15,000 or 80% of the Company's eligible accounts receivable.
Letter of credit	1,293,000						1,293,000
Revolving Credit Facility [Member] | Common Stock [Member]
Line of Credit Facility [Line Items]
Common stock per share	$ 2.70						$ 2.70
Fair value of warrant assumptions, expected volatility							57.00%
Fair value of warrant assumptions, risk free interest rate							2.10%
Fair value of warrant assumptions, expected life							10 years
Fair value of warrant assumptions, dividends							$ 0
Number of shares purchased from issuance of a warrant	37						37
Expiration date							Nov. 30, 2021
Aggregate estimated fair value of warrant							139,000
Supplemental Equipment Advance [Member]
Line of Credit Facility [Line Items]
Increase in the revolving credit facility			3,000,000					3,000,000
Revolving credit facility, amended annual interest rate								3.00%
Frequency of payments, description	Repayable in 33 consecutive monthly installments of principal and interest
Number of monthly installments								33
Revolving credit facility, the expiration date								Mar. 01, 2016
Supplemental Equipment Advance [Member] | Warrant [Member]
Line of Credit Facility [Line Items]
Common stock per share	$ 12.15						$ 12.15
Fair value of warrant assumptions, expected volatility	57.00%
Fair value of warrant assumptions, risk free interest rate	1.65%
Fair value of warrant assumptions, expected life	10 years
Fair value of warrant assumptions, dividends	$ 0
Number of shares purchased from issuance of a warrant	27						27		68
Expiration date	Dec. 31, 2022
Aggregate estimated fair value of warrant	213,000
Loan and Security Agreement [Member] | Series B [Member]
Line of Credit Facility [Line Items]
Number of shares called by issuance of warrant	51						51
Common stock per share	$ 2.7563						$ 2.7563
Expiration date of warrant	Oct. 30, 2018
Expiration period of warrant	5 years
Aggregate estimated fair value of warrant	72,000						72,000
Fair value of warrant assumptions, expected volatility	53.00%
Fair value of warrant assumptions, risk free interest rate	4.85%
Fair value of warrant assumptions, expected life	10 years
Fair value of warrant assumptions, dividends	$ 0
Computer Equipment [Member]
Line of Credit Facility [Line Items]
Effective interest rate										6.00%
Number of monthly installments										36
Net book value of equipment under capital lease	1,439,000						1,439,000
Remaining principal balance payable	$ 1,542,000						$ 1,542,000