Income Tax Provision (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Mar. 31, 2012
Deferred tax assets:
Reserves for expected costs of liquidation	$ 25,004
Net operating losses	19,263
Gross deferred tax assets	44,267
Deferred tax liabilities:
Fair value in excess of tax basis of holdings of New GM Securities	(236,624)
Gross deferred tax liabilities	(236,624)
Net deferred tax liability	$ (192,357)	$ (108,583)