Plan of Liquidation - Additional Information (Detail) - USD ($)			6 Months Ended	50 Months Ended	52 Months Ended
	Sep. 30, 2020	Apr. 30, 2020	Sep. 30, 2020	Jan. 31, 2020	Aug. 05, 2015	Jul. 01, 2019	Mar. 31, 2012	Dec. 15, 2011	Mar. 31, 2011
Class of Warrant or Right [Line Items]
Allowed General Unsecured Claims									$ 29,771,000,000
Disputed General Unsecured Claims	$ 0		$ 0						8,154,000,000
Total aggregate amount of general unsecured claims, both allowed and disputed inclusive of potential Term Loan Avoidance Action Claims									39,425,000,000
Amount of Term Loan Avoidance Action									1,500,000,000
Dividends received					$ 24,700,000
Contribution from MLC									52,700,000
Initial Reporting Cash									$ 5,700,000
Appropriated Distributable Cash	2,000,000			$ 58,800,000
Distributable Cash set aside for projected Trust fees, costs and expenses	34,300,000		34,300,000
Residual Wind-Down Assets	200,000		200,000					$ 42,800,000
Cash received to fund Avoidance Action Defense Costs								1,400,000
Residual wind-down assets transferred benefit in prepaid expenses								2,800,000
Avoidance action defense costs in excess of corresponding cash	30,200,000		30,200,000
Funds for Indenture Trustee/Fiscal Paying Agent Costs	100,000		100,000
Cash received for indenture trustee and paying agent costs								1,400,000
Cash received for funding Indenture Trustee Fiscal and Paying Agent Costs and Reporting Costs								3,400,000
Cash received for reporting cash	0		0					2,000,000
Distributions payable for new allowed general unsecured claims						$ 68,500,000
Recoveries by the avoidance action trust and corresponding new allowed general unsecured claims						$ 231,000,000
Not Yet Appropriated Distributable Cash	48,000,000
Approved Motion For Appropriation Of Distributable Cash		$ 50,000,000
Effect on Distributable Cash and Other Adminstrative Cash Upon Appropriation	48,000,000		48,000,000
Avoidance ActionTrust [Member]
Class of Warrant or Right [Line Items]
Resolved Term Loan Avoidance Action Claims distributions paid	67,800,000		67,800,000
New GM Securities [Member]
Class of Warrant or Right [Line Items]
Aggregate sales of new GM Securities to fund costs and expenses					61,700,000
Aggregate dividend cash associated with sales of New GM Securities to fund costs					$ 200,000
Cash and Cash Equivalents and Marketable Securities [Member]
Class of Warrant or Right [Line Items]
Remaining Administrative Fund aggregated	1,145,000		1,145,000
Aggregate Other Administrative Cash	29,563,000		29,563,000
Residual Wind-Down Assets	178,000		178,000					$ 40,000,000
Funds for Indenture Trustee/Fiscal Paying Agent Costs	$ 90,000		$ 90,000
New GM Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Distributable assets number of securities called by warrants									136,363,635
Exercise price per share									$ 10.00
Warrants expiration date			Jul. 10, 2016
Number of securities sold to fund costs and expenses					948,887
New GM Series B Warrants [Member]
Class of Warrant or Right [Line Items]
Distributable assets number of securities called by warrants									136,363,635
Exercise price per share									$ 18.33
Warrants expiration date			Jul. 10, 2019
Number of securities sold to fund costs and expenses					948,887
New GM Common Stock [Member]
Class of Warrant or Right [Line Items]
Distributable assets number of securities									150,000,000
Securities authorized for sale							$ 13,700,000
Number of securities sold to fund costs and expenses					1,043,801