Income Tax Benefit (Provision) - Summary of Deferred Taxes (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Deferred tax assets:
Reserves for expected costs of liquidation	$ 13,414	$ 21,983
Net operating and capital loss carryovers	106,867	18,212
Gross deferred tax assets	120,281	40,195
Less: Valuation allowance	(71,197)
Deferred tax asset, net of valuation allowance	49,084	40,195
Deferred tax liabilities:
Fair value in excess of tax basis of holdings of New GM Securities	(49,084)	(205,040)
Gross deferred tax liabilities	(49,084)	(205,040)
Net deferred tax liability		$ (164,845)