Derivative and Other Financial Instruments and Fair Value Measurements - Additional Information (Detail) $ / shares in Units, BTU in Trillions			3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 27, 2015	Jun. 11, 2010 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) BTU kt $ / shares shares	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) $ / shares	Sep. 30, 2016 EUR (€)	Feb. 28, 2015 $ / shares
Derivatives
Derivative contracts outstanding | kt					21,200
Cash collateral posted or held			$ 0		$ 0
Amount subject to enforceable master netting arrangement not offset			$ 0		$ 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
Common stock warrants percentage vested		100.00%
Common stock warrants expiration date					2020-06
Price per share of common stock issued | $ / shares									$ 5.64
Warrants exercised | shares					0
Warrants outstanding | shares			1,448,333		1,448,333
Redeemable Preferred Stock
Derivatives
Temporary equity redemption period	66 months				35 months
Credit spread adjustment percentage					16.00%
Maximum
Derivatives
Number of days financing receivable is estimated to be outstanding					30 days
Factoring Facility
Derivatives
Maximum financing amount | €								€ 50,000,000
Sales of trade accounts receivable			$ 102,300,000	$ 96,700,000	$ 290,800,000	$ 270,200,000
Proceeds from sales of trade accounts receivable			105,100,000	92,700,000	288,700,000	262,700,000
Administrative fees and expenses associated with Factoring Facility			$ 200,000	$ 200,000	$ 600,000	$ 600,000
Common Stock Warrant Liability
Derivatives
Valuation technique					Monte Carlo simulation
Volatility					66.20%		47.10%
Expected term					2 years 8 months 12 days		3 years 4 months 24 days
Equity raise probability					60.00%		60.00%
Equity raise price discount assumption					25.00%		25.00%
Common stock price on measurement date | $ / shares			$ 1.80		$ 1.80		$ 6.10
Percentage of increase decrease in unobservable inputs on estimated fair value of common stock warrant liability					10.00%
Currency Exchange Hedging
Derivatives
Currency derivative contracts outstanding			$ 0		$ 0
Natural Gas | Swap Contract One | Long
Derivatives
Forward buy contracts outstanding | BTU					1.6