Nature of Operations and Basis of Presentation - Narrative (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2020	Mar. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards (Note 1)		$ (660)
Accounting Standards Update 2016-13 [Member] \| Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards (Note 1)	$ 660
GM Financial [Member] \| Accounting Standards Update 2016-13 [Member] \| Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards (Note 1)	643
GM Financial [Member] \| Accounting Standards Update 2016-13 [Member] \| Credit Losses [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards (Note 1)	$ 801