Condensed Consolidated Statement of Cash Flows (unaudited) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020
Operating activities
Net income (loss)		$ 1,696	$ (78)
Reconciliation of net income (loss) to net cash provided by operating activities
Depreciation and amortization		640	802
Goodwill impairment		0	50
Provision for credit losses		(45)	1,190
Gain on mortgage and automotive loans, net		(55)	(2)
Other gain on investments, net		(188)	(109)
Loss on extinguishment of debt		74	1
Originations and purchases of loans held-for-sale		(2,154)	(1,329)
Proceeds from sales and repayments of loans held-for-sale		2,230	1,167
Net change in
Deferred income taxes		(675)	0
Interest payable		(48)	56
Other assets		2	(420)
Other liabilities		231	(211)
Other, net		(86)	45
Net cash provided by operating activities		1,622	1,162
Investing activities
Purchases of equity securities		(724)	(740)
Proceeds from sales of equity securities		944	774
Purchases of available-for-sale securities		(14,376)	(7,696)
Proceeds from sales of available-for-sale securities		2,788	5,544
Proceeds from repayments of available-for-sale securities		6,539	4,440
Purchases of held-to-maturity securities		(97)	0
Proceeds from repayments of held-to-maturity securities		223	177
Purchases of finance receivables and loans held-for-investment		(3,500)	(3,495)
Proceeds from sales of finance receivables and loans initially held-for-investment		376	1
Originations and repayments of finance receivables and loans held-for-investment and other, net		9,095	13,135
Purchases of operating lease assets		(3,026)	(1,949)
Disposals of operating lease assets		1,775	1,179
Net change in nonmarketable equity investments		93	148
Other, net		(201)	(213)
Net cash (used in) provided by investing activities		(91)	11,305
Financing activities
Net change in short-term borrowings		(2,136)	(1,842)
Net increase in deposits		2,060	10,272
Proceeds from issuance of long-term debt		194	2,372
Repayments of long-term debt		(3,800)	(7,434)
Repurchases of common stock		(721)	(104)
Preferred stock issuance		2,326	0
Trust preferred securities redemption		(1,442)	0
Dividends paid		(144)	(144)
Net cash (used in) provided by financing activities		(3,663)	3,120
Effect of exchange-rate changes on cash and cash equivalents and restricted cash		3	(3)
Net (decrease) increase in cash and cash equivalents and restricted cash		(2,129)	15,584
Cash and cash equivalents and restricted cash at beginning of year		16,574	4,380
Cash and cash equivalents and restricted cash at June 30,		14,445	19,964
Supplemental disclosures
Interest		1,057	1,722
Income taxes		1,212	7
Loans held-for-sale transferred to finance receivables and loans held-for-investment		5	70
Additions of property and equipment		46	0
Finance receivables and loans held-for-investment transferred to loans held-for-sale		414	0
In-kind distribution from equity-method investee		0	60
Equity consideration received in exchange for restructured loans		0	5
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents on the Condensed Consolidated Balance Sheet		13,664	19,131
Restricted cash included in other assets on the Condensed Consolidated Balance Sheet	[1]	781	833
Total cash and cash equivalents and restricted cash in the Condensed Consolidated Statement of Cash Flows		$ 14,445	$ 19,964

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