Operations - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2012
Brokers and Dealers Disclosure [Line Items]
Redemption penalty if redemption is made during first 11 months	1.50%
Written notice period for redemption	5 days
Number of business days redemption required to make payment	10 days
Class A
Brokers and Dealers Disclosure [Line Items]
Brokerage fee	4.67%
Class A | Annual Payment Rate
Brokers and Dealers Disclosure [Line Items]
Brokerage fee	4.67%
Class A | Monthly Payment Rate
Brokers and Dealers Disclosure [Line Items]
Brokerage fee	0.38917%
Class B
Brokers and Dealers Disclosure [Line Items]
Brokerage fee	2.67%
Class B | Annual Payment Rate
Brokers and Dealers Disclosure [Line Items]
Brokerage fee	2.67%
Class B | Monthly Payment Rate
Brokers and Dealers Disclosure [Line Items]
Brokerage fee	0.2225%