Commitments and Contingencies - Additional Information (Detail) (USD $)	May 13, 2011	May 12, 2011
Commitments and Contingencies Disclosure [Line Items]
Irrevocable letter of credit delivered as a security for lease obligation	$ 2,400,000
Irrevocable letter of credit		2,600,000
Irrevocable letter of credit, maturity date		2012-05
Irrevocable letter of credit, additional amount for potential market fluctuation		200,000
On the fifth anniversary of the lease commencement date
Commitments and Contingencies Disclosure [Line Items]
Irrevocable letter of credit delivered as a security for lease obligation	$ 1,200,000