Holdings of New GM Securities at March 31, 2015 - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 31, 2015
Summary of Investment Holdings [Line Items]
Liquidating distributions payable in cash	$ 6,200	$ 200
New GM Securities reserved and set aside for projected GUC Trust fees, costs and expenses		67,500
New GM Securities set aside for potential Taxes on Distribution		297,200
Projected Dividend Taxes		19,400
Liquidation Basis of Accounting [Member]
Summary of Investment Holdings [Line Items]
Liquidating distributions payable	$ 6,213	7,714
New GM Securities [Member] | Liquidation Basis of Accounting [Member]
Summary of Investment Holdings [Line Items]
Liquidating distributions payable		$ 7,700
New GM Common Stock [Member]
Summary of Investment Holdings [Line Items]
Number of warrants or shares pending distribution		93,114
Number of securities set aside from distribution		4,525,790
New GM Series A Warrants [Member]
Summary of Investment Holdings [Line Items]
Number of warrants or shares pending distribution		84,570
Number of warrants set aside from distribution		4,114,331
New GM Series B Warrants [Member]
Summary of Investment Holdings [Line Items]
Number of warrants or shares pending distribution		84,570
Number of warrants set aside from distribution		4,114,331