Holdings of New GM Securities - Securities Pending Distribution or Set Aside (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014
Distribution Made to Limited Partner [Line Items]
Fair Value	$ 664,867
New GM Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Number	8,594,127
Fair Value	311,967
New GM Series A Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number	7,812,711
Fair Value	207,896
New GM Series B Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number	7,812,711
Fair Value	$ 145,004