Derivative and Other Financial Instruments and Fair Value Measurements - Additional Information (Detail) $ / shares in Units, BTU in Trillions		1 Months Ended			12 Months Ended
	Jun. 11, 2010 USD ($) $ / shares shares	Apr. 30, 2016 shares	Sep. 30, 2015 shares	May 31, 2015 USD ($) shares	Dec. 31, 2016 USD ($) BTU t $ / shares shares	Dec. 31, 2015 USD ($) BTU t	Jun. 30, 2015	Feb. 28, 2015 $ / shares	Dec. 31, 2014 Derivative
Derivative [Line Items]
Derivative contracts | t					27,100	24,600
Cash collateral posted or held | $					$ 0
Amount subject to enforceable master netting arrangement not offset | $					$ 0	$ 0
Warrant issued to purchase common stock | shares	1,500,000
Aggregate purchase price of common stock warrant | $	$ 300,000
Exercise price of warrants | $ / shares	$ 10.30				$ 5.64			$ 5.64
Warrant vested upon issuance							20.00%
Common stock warrants vesting percentage on each anniversary date							20.00%
Common stock warrants percentage vested							100.00%
Common stock warrants expiration date					2020-06
Warrants exercised on cashless basis | shares		20,000	16,667	15,000
Warrants issued on cashless basis | shares				7,500
Proceeds from issuance of common stock for warrants exercised | $				$ 100,000
Warrants outstanding | shares					1,448,333
Number of derivative instruments held | Derivative									0
Redeemable Preferred Stock
Derivative [Line Items]
Valuation technique					Hull & White model
Equity raise probability of weighted average price on volume days					10 days
Preferred stock redemption period					66 months
Credit spread adjustment percentage					17.50%
Maximum
Derivative [Line Items]
Number of days financing receivable is estimated to be outstanding					30 days
Maximum | Redeemable Preferred Stock
Derivative [Line Items]
Equity raise price discount assumption					25.00%
Minimum | Redeemable Preferred Stock
Derivative [Line Items]
Equity raise price discount assumption					15.00%
Warrants
Derivative [Line Items]
Common stock issued, Shares | shares		7,552	6,969	9,360
Common Stock Warrant Liability
Derivative [Line Items]
Valuation technique					Monte Carlo Simulation
Volatility					47.10%	49.90%
Expected term					3 years 4 months 24 days	4 years 4 months 24 days
Equity raise probability					60.00%	60.00%
Equity raise price discount assumption					25.00%	15.00%
Percentage of increase decrease in unobservable inputs on estimated fair value of common stock warrant liability					10.00%
Equity raise probability of weighted average price on volume days					10 days	10 days
NABCO
Derivative [Line Items]
Price per share of common stock issued | $ / shares								$ 5.64
Currency Exchange Hedging
Derivative [Line Items]
Currency derivative contracts outstanding | $					$ 0	$ 0
Natural Gas | Swap Contract One | Long
Derivative [Line Items]
Forward buy contracts | BTU					1.8	1.9