Holdings of New GM Securities - Additional Information (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable in cash	$ 200,000	$ 200,000
New GM Securities reserved and set aside for projected GUC Trust fees, costs and expenses	67,500,000	51,600,000
New GM Securities set aside for potential Taxes on Distribution	297,200,000	536,300,000
Projected Dividend Taxes	19,400,000	3,500,000
Liquidation Basis of Accounting [Member]
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable	7,714,000	42,111,000
New GM Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	93,114	575,278
Number of securities set aside from distribution	4,525,790	8,072,042
New GM Series A Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	84,570	522,865
Number of warrants set aside from distribution	4,114,331	7,338,194
New GM Series B Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	84,570	522,865
Number of warrants set aside from distribution	4,114,331	7,338,194
New GM Securities [Member]
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable in cash	$ 200,000