Holdings of New GM Securities (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2012
New GM Securities Pending Distribution Or Set Aside
Fair Value	$ 297,045
New GM Common Stock [Member]
New GM Securities Pending Distribution Or Set Aside
Number	6,942,556
Fair Value	157,943
New GM Series A Warrants [Member]
New GM Securities Pending Distribution Or Set Aside
Number	6,311,320
Fair Value	86,970
New GM Series B Warrants [Member]
New GM Securities Pending Distribution Or Set Aside
Number	6,311,320
Fair Value	$ 52,132