Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Inventory [Line Items]
Total productive material, supplies and work in process	$ 5,807	$ 5,380
Finished product, including service parts	8,561	8,262
Total inventories	14,368	13,642
GMNA [Member]
Inventory [Line Items]
Total productive material, supplies and work in process	3,136	2,592
Finished product, including service parts	4,215	4,320
Total inventories	7,351	6,912
GME [Member]
Inventory [Line Items]
Total productive material, supplies and work in process	751	778
Finished product, including service parts	2,250	2,394
Total inventories	3,001	3,172
GMIO [Member]
Inventory [Line Items]
Total productive material, supplies and work in process	1,193	1,216
Finished product, including service parts	1,104	1,026
Total inventories	2,297	2,242
GMSA [Member]
Inventory [Line Items]
Total productive material, supplies and work in process	727	794
Finished product, including service parts	992	522
Total inventories	$ 1,719	$ 1,316