Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Observable Inputs (Level 2) (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Change in fair value included in earnings	$ 73,000	$ (44,000)	$ (35,000)	$ (474,000)
Fair Value, Measurements, Recurring | Warrants | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance			354,000
Change in fair value included in earnings			35,000
Exercise of warrants			(64,000)
Balance	$ 325,000		$ 325,000