Leases - Summary of Selected Financial Data (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Total revenue	$ 24,014	$ 24,692	$ 71,911	$ 70,136
Net income (loss)	10,235	41,877	26,510	64,966
CPD NY and NECG [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenue	144,942	143,191	419,338	410,182
Gross profit	12,130	10,054	32,313	29,841
Net income (loss)	541	1,243	1,240	2,702
Current assets	12,579		12,579		10,944
Noncurrent assets	30,096		30,096		28,852
Current liabilities	15,624		15,624		13,985
Noncurrent liabilities	16,043		16,043		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	89,830	91,135	266,933	268,880
Gross profit	2,341	2,338	5,753	9,724
Net income (loss)	(870)	(783)	(3,918)	(1,363)
Current assets	6,254		6,254		10,128
Noncurrent assets	108,808		108,808		111,540
Current liabilities	8,578		8,578		10,880
Noncurrent liabilities	$ 135,383		$ 135,383		$ 135,210