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Income Taxes - Schedule of Difference in Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Apr. 30, 2014	Apr. 30, 2013
Income Loss From Operations Before Provision Benefit For Income Taxes [Line Items]
Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Tax at statutory rate	$ (1,787)	$ (3,650)	$ (8,929)	$ (18,378)
State income taxes, net of federal benefit	(59)	198	(1,271)	(1,076)
Non-deductible expenses	505	467	505	494
Tax credits	(380)	(671)	(598)	(660)
Non-deductible equity income in subsidiaries and GreenFiber goodwill impairment	(73)	(415)	1,548	180
Tax over book basis in GreenFiber on sale			(2,570)
Other, net	(35)	150	(491)	(512)
Income before provision (benefit) for income tax, net	703	1,351	1,799	(2,526)
Other Valuation Allowance [Member]
Income Loss From Operations Before Provision Benefit For Income Taxes [Line Items]
Increase (decrease) in valuation allowance	$ 2,532	$ 5,272	$ 13,605	22,510
Business Acquisition [Member]
Income Loss From Operations Before Provision Benefit For Income Taxes [Line Items]
Increase (decrease) in valuation allowance				$ (5,084)

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Income Loss From Operations Before Provision Benefit For Income Taxes [Line Items]

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to nondeductible expenses.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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