Financial Instruments, Measured at Fair Value, by Level within Fair Value Hierarchy (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Warrant liability	$ 354,000	$ 615,000
Fair Value, Inputs, Level 1
Warrant liability	0	0
Fair Value, Inputs, Level 2
Warrant liability	354,000	615,000
Fair Value, Inputs, Level 3
Warrant liability	$ 0	$ 0