Income Tax Provision - Summary of Deferred Taxes (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014
Deferred tax assets:
Reserves for expected costs of liquidation	$ 11,686
Net operating and capital loss carryovers	106,473
Gross deferred tax assets	118,159
Less: Valuation allowance	(112,469)
Deferred tax asset, net of valuation allowance	5,690
Deferred tax liabilities:
Fair value in excess of tax basis of holdings of New GM Securities	(4,256)
Other	(1,434)
Gross deferred tax liabilities	(5,690)
Net deferred tax liability	$ 0