Series D Preferred Shares - Additional Information (Detail)					3 Months Ended
	Mar. 19, 2018 USD ($) shares	Mar. 16, 2018 USD ($)	Jun. 22, 2017 USD ($) shares	Dec. 07, 2016 USD ($) shares	Mar. 31, 2018 USD ($) shares	Dec. 31, 2017 shares	Oct. 18, 2017 USD ($)	Oct. 17, 2017 USD ($)	Oct. 11, 2017 USD ($)	Dec. 31, 2015 shares	Sep. 30, 2015 USD ($) Covenant	Oct. 01, 2012 USD ($) $ / shares shares
Temporary Equity [Line Items]
Aggregate purchase price under Securities Purchase Agreement | $					$ 100,000,000
Stock Appreciation Rights												6,735,667
Net proceeds from portion of assets sold | $		$ 4,863,000
Adjusted
Temporary Equity [Line Items]
Warrants exercisable for common shares					11,035,875
Stock Appreciation Rights					7,485,045
ARS VI
Temporary Equity [Line Items]
Aggregate purchase price under Securities Purchase Agreement | $												$ 100,000,000
ARS VI | Warrants and investor SARs
Temporary Equity [Line Items]
Class of warrant and right exercise of purchase value. | $									$ 20,500,000
Fair value adjustment of warrants and investor rights obligation | $							$ 0
Warrants and rights outstanding | $								$ 0
Preferred Series D
Temporary Equity [Line Items]
Cumulative redeemable preferred shares, shares issued	2,939,190		3,133,720	3,536,000		3,133,720				4,000,000
Preferred shares with warrants												9,931,000
Shares repurchased and cancelled, shares	194,530		402,280	464,000
Repurchased shares price | $	$ 4,863,000		$ 10,057,000	$ 11,600,000
Cumulative redeemable preferred shares, shares outstanding	2,939,190		3,133,720	3,536,000		3,133,720				4,000,000
Shares redeem and cancel, shares					194,530
Preferred Series D | ARS VI
Temporary Equity [Line Items]
Cumulative redeemable preferred shares, shares issued												4,000,000
Cumulative Redeemable Preferred Shares, par value | $ / shares												$ 0.01
Number of covenants | Covenant											2
Consideration paid under Securities Purchase Agreement | $											$ 450,000