Summary of Convertible Debt and Initial Accounting of Issuances (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	$ 2,210	$ 2,100
Initial Accounting One
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	1,300
Initial Accounting Two
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	400
Initial Accounting Three
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	400
Initial Accounting Four
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	2,460
Stock Warrants | Initial Accounting One
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	(168)
Stock Warrants | Initial Accounting Two
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	(105)
Stock Warrants | Initial Accounting Three
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	(96)
Stock Warrants | Initial Accounting Four
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	(331)
Embedded conversion derivative liability | Initial Accounting One
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	(1,132)
Embedded conversion derivative liability | Initial Accounting Two
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	(295)
Embedded conversion derivative liability | Initial Accounting Three
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	(304)
Embedded conversion derivative liability | Initial Accounting Four
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	(2,129)
Total | Initial Accounting One
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	0
Total | Initial Accounting Two
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	0
Total | Initial Accounting Three
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	0
Total | Initial Accounting Four
Debt Instrument [Line Items]
Proceeds from convertible debt issuance	$ 0