Holdings of New GM Securities (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012
New GM Securities Pending Distribution Or Set Aside
Fair Value	$ 233,418
New GM Common Stock [Member]
New GM Securities Pending Distribution Or Set Aside
Number	6,501,366
Fair Value	128,207
New GM Series A Warrants [Member]
New GM Securities Pending Distribution Or Set Aside
Number	5,910,257
Fair Value	65,139
New GM Series B Warrants [Member]
New GM Securities Pending Distribution Or Set Aside
Number	5,910,257
Fair Value	$ 40,072