Holdings of New GM Securities - Additional Information (Detail) (USD $)	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2013 New GM Common Stock [Member]	Sep. 26, 2013 New GM Common Stock [Member]	Sep. 30, 2013 New GM Series A Warrants [Member]	Sep. 26, 2013 New GM Series A Warrants [Member]	Sep. 30, 2013 New GM Series B Warrants [Member]	Sep. 26, 2013 New GM Series B Warrants [Member]	Sep. 26, 2013 GUC Trust Units [Member]
Distribution Made to Limited Partner [Line Items]
Liquidating distributions payable	$ 100,447,000	$ 16,555,000
Liquidating distributions payable in cash	13,000
Number of warrants or shares pending distribution			1,306,105		1,187,320		1,187,320
New GM Securities reserved and set aside for projected GUC Trust fees, costs and expenses	67,800,000
New GM securities set aside for potential taxes on distribution	$ 572,700,000
Number of securities set aside from distribution			8,329,297
Number of warrants set aside from distribution					7,572,064		7,572,064
Proposed settlement Distribution of shares				6,174,015
Proposed settlement Distribution of Warrants						5,612,741		5,612,741
Proposed Settlement Distribution of Trust Units									1,550,000