Condensed Consolidated Statement of Cash Flows (unaudited) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net income		$ 2,408	$ 398
Reconciliation of net income to net cash provided by operating activities
Depreciation and amortization		931	1,159
Goodwill impairment		0	50
Provision for credit losses		31	1,337
Gain on mortgage and automotive loans, net		(73)	(35)
Other gain on investments, net		(212)	(173)
Loss on extinguishment of debt		126	50
Originations and purchases of loans held-for-sale		(3,136)	(2,241)
Proceeds from sales and repayments of loans held-for-sale		3,186	2,107
Net change in
Deferred income taxes		(558)	122
Interest payable		10	107
Other assets		19	(196)
Other liabilities		419	(29)
Other, net		(68)	(52)
Net cash provided by operating activities		3,083	2,604
Investing activities
Purchases of equity securities		(1,117)	(816)
Proceeds from sales of equity securities		1,280	936
Purchases of available-for-sale securities		(17,211)	(12,013)
Proceeds from sales of available-for-sale securities		4,870	6,350
Proceeds from repayments of available-for-sale securities		8,725	7,846
Purchases of held-to-maturity securities		(201)	0
Proceeds from repayments of held-to-maturity securities		303	306
Purchases of finance receivables and loans held-for-investment		(5,466)	(5,188)
Proceeds from sales of finance receivables and loans initially held-for-investment		376	122
Originations and repayments of finance receivables and loans held-for-investment and other, net		8,669	14,745
Purchases of operating lease assets		(4,231)	(3,226)
Disposals of operating lease assets		2,618	1,946
Net change in nonmarketable equity investments		104	305
Other, net		(294)	(308)
Net cash (used in) provided by investing activities		(1,575)	11,005
Financing activities
Net change in short-term borrowings		(2,136)	(2,499)
Net increase in deposits		2,398	14,168
Proceeds from issuance of long-term debt		253	3,174
Repayments of long-term debt		(4,812)	(11,887)
Purchases of land and buildings in satisfaction of finance lease liabilities		(391)	0
Repurchases of common stock		(1,400)	(105)
Preferred stock issuance		2,324	0
Trust preferred securities redemption		(2,513)	0
Common stock dividends paid		(237)	(217)
Preferred stock dividends paid		(29)	0
Net cash (used in) provided by financing activities		(6,543)	2,634
Effect of exchange-rate changes on cash and cash equivalents and restricted cash		0	(1)
Net (decrease) increase in cash and cash equivalents and restricted cash		(5,035)	16,242
Cash and cash equivalents and restricted cash at beginning of year		16,574	4,380
Cash and cash equivalents and restricted cash at September 30,		11,539	20,622
Cash paid for
Interest		1,422	2,414
Income taxes		1,235	8
Noncash items
Loans held-for-sale transferred to finance receivables and loans held-for-investment		5	74
Additions of property and equipment		46	0
Finance receivables and loans held-for-investment transferred to loans held-for-sale		414	128
In-kind distribution from equity-method investee		0	126
Equity consideration received in exchange for restructured loans		0	5
Decrease in held-to-maturity securities due to the consolidation of a VIE		0	5
Increase in held-for-investment loans and other, net, due to the consolidation of a VIE		0	114
Increase in collateralized borrowings, net, due to the consolidation of a VIE		0	109
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents on the Condensed Consolidated Balance Sheet		10,915	19,939
Restricted cash included in other assets on the Condensed Consolidated Balance Sheet	[1]	624	683
Total cash and cash equivalents and restricted cash in the Condensed Consolidated Statement of Cash Flows		$ 11,539	$ 20,622

[1] Restricted cash balances relate primarily to Ally securitization arrangements. Refer to Note 10 for additional details describing the nature of restricted cash balances.