Holdings of New GM Securities (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013
New GM Securities Pending Distribution or Set Aside
Fair Value	$ 631,343
New GM Common Stock [Member]
New GM Securities Pending Distribution or Set Aside
Number	9,020,282
Fair Value	300,466
New GM Series A Warrants [Member]
New GM Securities Pending Distribution or Set Aside
Number	8,200,178
Fair Value	196,804
New GM Series B Warrants [Member]
New GM Securities Pending Distribution or Set Aside
Number	8,200,178
Fair Value	$ 134,073