Offering Costs and Formation Transaction Expenses - Effect of Deferred Costs and Formation Transaction Expenses on Financial Statements (Detail) (USD $)	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Deferred costs, net	$ 3,020,383			$ 3,020,383		$ 1,684,758
Members' deficiency						(13,296,760)
Formation transaction expenses	108,931	143,263	82,822	191,753	192,484
Net income (loss)	5,063,461	2,826,340	(502,684)	4,560,777	2,624,363	2,283,399
Net cash provided by (used in) operating activities			1,047,587	(663,612)	2,594,457
Net cash used in financing activities			(3,690,570)	(4,882,642)	(3,156,740)
Net change in cash and cash equivalents			(3,590,915)	(7,166,008)	(1,478,729)
As reported [Member]
Deferred costs, net						2,140,059
Members' deficiency						(12,841,459)
Net income (loss)		2,969,603	(419,862)		2,816,847
Net cash provided by (used in) operating activities			1,130,409		2,786,941
Net cash used in financing activities			(3,773,392)		(3,349,224)
Net change in cash and cash equivalents			(3,590,915)		(1,478,729)
Adjustment [Member]
Deferred costs, net						(455,301)
Members' deficiency						(455,301)
Formation transaction expenses		143,263	82,822		192,484
Net income (loss)		(143,263)	(82,822)		(192,484)
Net cash provided by (used in) operating activities			(82,822)		(192,484)
Net cash used in financing activities			$ 82,822		$ 192,484