Changes in Fair Value of Derivative Instrument Liabilities using Level 3 Inputs (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 600,000
Origination of derivative instrument	705,000
Adjustments resulting from change in value of underlying asset and passage of time recognized in earnings	(87,000)
Ending Balance	1,218,000
October 27, 2006
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	597,000
Origination of derivative instrument	0
Adjustments resulting from change in value of underlying asset and passage of time recognized in earnings	19,000
Ending Balance	616,000
Sept 29, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,000
Origination of derivative instrument	0
Adjustments resulting from change in value of underlying asset and passage of time recognized in earnings	(2,000)
Ending Balance	1,000
October 12, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0
Origination of derivative instrument	705,000
Adjustments resulting from change in value of underlying asset and passage of time recognized in earnings	(104,000)
Ending Balance	$ 601,000