Holdings of New GM Securities (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012
New GM Securities Pending Distribution or Set Aside
Fair Value	$ 463,041
New GM Common Stock [Member]
New GM Securities Pending Distribution or Set Aside
Number	7,995,690
Fair Value	230,516
New GM Series A Warrants [Member]
New GM Securities Pending Distribution or Set Aside
Number	7,268,692
Fair Value	141,739
New GM Series B Warrants [Member]
New GM Securities Pending Distribution or Set Aside
Number	7,268,692
Fair Value	$ 90,786