Holdings of New GM Securities - Securities Pending Distribution or Set Aside (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013
Distribution Made to Limited Partner [Line Items]
Fair Value	$ 767,363
New GM Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Number	8,507,643
Fair Value	347,707
New GM Series A Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number	7,734,157
Fair Value	240,842
New GM Series B Warrants [Member]
Distribution Made to Limited Partner [Line Items]
Number	7,734,157
Fair Value	$ 178,814