Income Tax Provision (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Deferred tax assets:
Reserves for expected costs of liquidation	$ 21,983	$ 24,539
Net operating losses	18,212	9,537
Gross deferred tax assets	40,195	34,076
Deferred tax liabilities:
Fair value in excess of tax basis of holdings of New GM Securities	(205,040)	(142,659)
Gross deferred tax liabilities	(205,040)	(142,659)
Net deferred tax liability	$ (164,845)	$ (108,583)