Holdings of New GM Securities - Securities Pending Distribution or are Set Aside (Detail) - Jun. 30, 2015 - USD ($) $ in Thousands	Total
Distribution Made to Limited Partner [Line Items]
Fair Value	$ 320,154
New GM Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Number	4,610,631
Fair Value	$ 153,672
New GM Series A Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number	4,191,383
Fair Value	$ 99,629
New GM Series B Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number	4,191,383
Fair Value	$ 66,853