Significant Accounting Policies - Additional information (Detail) - USD ($)		12 Months Ended
	Nov. 04, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Determination of exploratory well's ability to produce, term		1 year
Sales revenue, crude oil and natural gas		$ 52,200,000	$ 63,000,000	$ 102,800,000
Liability for Uncertain Tax Positions, Current		$ 8,100,000	$ 10,900,000
Series A Preferred Shares [Member]
Significant Accounting Policies [Line Items]
Preferred shares, issued	921,000	510,000
Preferred stock, dividend rate, percentage	12.00%
Preferred stock, shares issued value per share	$ 50.00	$ 50
Series A Preferred Shares [Member] | 2017 Notes [Member]
Significant Accounting Policies [Line Items]
Preferred shares, issued	815,000
Proceeds from issuance of preferred stock	$ 40,750,000
Convertible preferred shares issued upon conversion	20
Value of principal amount on conversion	$ 1,000,000
Series A Preferred Shares [Member] | 2017 Notes [Member] | Certain Holders [Member]
Significant Accounting Policies [Line Items]
Preferred shares, issued	106,000
Proceeds from issuance of preferred stock	$ 5,300,000
Sales Revenue, Goods, Net [Member] | Revenue from Rights Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration Risk, Percentage		76.10%	74.00%	74.10%
Minimum [Member]
Significant Accounting Policies [Line Items]
Equipment and other property, estimated useful lives		3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Equipment and other property, estimated useful lives		7 years