Plan of Liquidation - Additional Information (Detail) - USD ($)	6 Months Ended	28 Months Ended	38 Months Ended	52 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Jan. 23, 2019	Aug. 05, 2015	Dec. 31, 2018	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			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
Reserve for remaining Disputed General Unsecured Claims					50,000,000
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		$ 35,600,000
Distributable Cash set aside for projected Trust fees, costs and expenses					24,800,000
Distributable Cash set aside for potential Taxes on Distribution					0
Residual Wind-Down Assets					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
Expected Residual Wind-Down Claims and Costs					0
Cash received for funding Indenture Trustee Fiscal and Paying Agent Costs and Reporting Costs							3,400,000
Cash received for indenture trustee and paying agent costs							1,400,000
Cash received for reporting cash					0		2,000,000
Subsequent Event [Member]
Class of Warrant or Right [Line Items]
Appropriated Distributable Cash			$ 12,400,000
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					1,279,000
Aggregate Other Administrative Cash					18,583,000
Residual Wind-Down Assets					174,000		$ 40,000,000
Funds for Indenture Trustee/Fiscal Paying Agent Costs					136,000
Marketable Securities [Member]
Class of Warrant or Right [Line Items]
Funds for Indenture Trustee/Fiscal Paying Agent Costs					$ 100,000
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