Summary of Unaudited Results of Operations and Financial Position of Equity Investments in Affiliates (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Investments In And Advances To Affiliates Schedule Of Investments [Abstract]
Net operating revenues	$ 23,035,340	$ 24,990,428
Net income	6,027,677	$ 6,159,449
Current assets	9,969,648		$ 12,371,752
Noncurrent assets	5,817,247		7,699,093
Total assets	15,786,895		20,070,845
Current liabilities	3,833,829		4,240,326
Noncurrent liabilities	1,540,610		2,266,793
Total liabilities	5,374,439		6,507,119
Members' equity	$ 10,412,456		$ 13,563,726