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Mandatorily Redeemable Series A Preferred Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jan. 31, 2012	Sep. 30, 2011	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 09, 2016
Class Of Stock [Line Items]
Common stock, shares issued			40,474,085	38,884,068
Interest expense incurred				$ 5,565	$ 5,078
Series A Preferred Stock
Class Of Stock [Line Items]
Redeemable Series A preferred stock						$ 40,329
Mandatorily Redeemable Series A Preferred Stock
Class Of Stock [Line Items]
Preferred stock, dividend rate per annum			15.00%
Preferred shares issued for dividends			0	4,776	4,865
Interest expense incurred			$ 0	$ 5,624	$ 5,652
Interest expense capitalized to property, plant and equipment			$ 0	$ 59	$ 574
Mandatorily Redeemable Series A Preferred Stock \| Installment One
Class Of Stock [Line Items]
Preferred Stock, Dividend Payment Terms			Dividends accrued and accumulated on the Series A Preferred Stock, whether or not earned or declared, at the rate of 15% per annum and compound quarterly on April 1, July 1, October 1 and January 1.
Series A Investor
Class Of Stock [Line Items]
Date of agreement			Sep. 13, 2011
Series A Investor \| Tranche One
Class Of Stock [Line Items]
Common stock, shares issued		14,300,000
Proceeds from issuance of common stock		$ 22,000
Series A Investor \| Mandatorily Redeemable Series A Preferred Stock \| Tranche One
Class Of Stock [Line Items]
Preferred stock, shares issued		22,000
Preferred stock issued, value per share		$ 1,000
Series A Investor \| Mandatorily Redeemable Series A Preferred Stock \| Tranche Two
Class Of Stock [Line Items]
Preferred stock, shares issued	26,000
Proceeds from issuance of redeemable preferred stock	$ 26,000