Holdings of New GM Securities - Additional Information (Detail) (USD $)	Sep. 30, 2014	Mar. 31, 2014
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable in cash	$ 3,400,000
New GM Securities reserved and set aside for projected GUC Trust fees, costs and expenses	59,000,000
New GM Securities set aside for potential Taxes on Distribution	247,800,000
Projected Dividend Taxes	5,700,000
Liquidation Basis of Accounting [Member]
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable	248,763,000	42,111,000
New GM Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	3,749,598
Number of securities set aside from distribution	4,687,818
New GM Series A Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	3,408,618
Number of warrants set aside from distribution	4,261,628
New GM Series B Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number of warrants or shares pending distribution	3,408,618
Number of warrants set aside from distribution	4,261,628
New GM Securities [Member]
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable	$ 245,400,000