Leases - Summary of Selected Financial Data (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Total revenue	$ 24,543	$ 24,072	$ 24,350	$ 23,757	$ 25,589	$ 28,067	$ 23,309	$ 22,430	$ 96,722	$ 96,269	$ 93,204
Net (loss) income	(3,092)	10,235	6,637	9,638	5,045	41,877	12,739	10,350	23,418	70,011	12,447
CPD NY and NECG [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									439,392	451,145	424,519
Gross profit									32,836	28,721	26,616
Net (loss) income									2,012	229	1,968
Current assets	13,520				10,944				13,520	10,944
Noncurrent assets	28,995				28,852				28,995	28,852
Current liabilities	2,531				13,985				2,531	13,985
Noncurrent liabilities	28,204				16,043				28,204	16,043
White Oak Petroleum, LLC, Hudson Petroleum Realty, LLC, Dogwood Petroleum Realty, LLC and Big Apple Petroleum Realty, LLC [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue									344,820	356,004	189,958
Gross profit									9,566	10,500	7,436
Net (loss) income									(3,343)	(4,011)	1,115
Current assets	9,288				9,165				9,288	9,165
Noncurrent assets	108,491				112,502				108,491	112,502
Current liabilities	13,793				10,880				13,793	10,880
Noncurrent liabilities	$ 134,700				$ 135,210				$ 134,700	$ 135,210