Holdings of New GM Securities - Additional Information (Detail) (USD $)	Dec. 31, 2014	Mar. 31, 2014
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable in cash	$ 200,000
New GM Securities reserved and set aside for projected GUC Trust fees, costs and expenses	68,400,000
New GM Securities set aside for potential Taxes on Distribution	271,200,000
Projected Dividend Taxes	8,100,000
Liquidation Basis of Accounting [Member]
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable	6,033,000	42,111,000
New GM Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	79,796
Number of securities set aside from distribution	4,641,667
New GM Series A Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	72,441
Number of warrants set aside from distribution	4,219,669
New GM Series B Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	72,441
Number of warrants set aside from distribution	4,219,669
New GM Securities [Member]
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable	$ 5,800,000