Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Inventory [Line Items]
Total productive material, supplies and work in process	$ 5,563	$ 5,380
Finished product, including service parts	8,655	8,262
Total inventories	14,218	13,642
GMNA [Member]
Inventory [Line Items]
Total productive material, supplies and work in process	2,830	2,592
Finished product, including service parts	4,112	4,320
Total inventories	6,942	6,912
GME [Member]
Inventory [Line Items]
Total productive material, supplies and work in process	702	778
Finished product, including service parts	2,571	2,394
Total inventories	3,273	3,172
GMIO [Member]
Inventory [Line Items]
Total productive material, supplies and work in process	1,175	1,216
Finished product, including service parts	1,091	1,026
Total inventories	2,266	2,242
GMSA [Member]
Inventory [Line Items]
Total productive material, supplies and work in process	856	794
Finished product, including service parts	881	522
Total inventories	$ 1,737	$ 1,316