Asset Retirement Obligations - Additional Information (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation [Abstract]
Capitalized asset retirement cost	$ 6,927,207	$ 6,481,752

The amount of asset retirement costs previously incurred and capitalized separately from the capitalized amount of the associated long-lived assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61901-109447

Name:	us-gaap_CapitalizedCostsAssetRetirementCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant