Parent Company Condensed Financial Information - Schedule of Condensed Statement of Cash Flows (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating activities
Net cash provided by operating activities		$ 1,266	$ 1,413	$ 2,720	$ 2,975	$ 3,577	$ 4,609	$ 4,528	$ 4,557	$ 6,247
Investing activities
Proceeds from sales of finance receivables and loans initially held-for-investment								1,400	258	55
Originations and repayments of finance receivables and loans held-for-investment and other, net								3,282	(5,040)	(7,927)
Proceeds from sales of equity securities								915	356	846
Net change in nonmarketable equity investments								84	(73)	27
Other, net								(608)	(579)	(531)
Net cash provided by (used in) investing activities		3,576	(363)	2,590	(2,435)	3,785	(4,144)	4,991	(7,182)	(17,263)
Financing activities
Proceeds from issuance of long-term debt								4,337	5,705	7,125
Repayments of long-term debt								(4,484)	(4,595)	(6,464)
Repurchases of common stock								(38)	(33)	(1,650)
Common stock dividends paid								(372)	(368)	(384)
Preferred stock dividends paid								(110)	(110)	(110)
Net cash (used in) provided by financing activities								(5,566)	3,839	11,575
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net increase (decrease) in cash and cash equivalents and restricted cash								3,941	1,217	552
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash at beginning of year		7,439	6,222	7,439	6,222	7,439	6,222	7,439	6,222	5,670
Cash and cash equivalents and restricted cash at December 31,								11,380	7,439	6,222
Restricted Cash [Abstract]
Cash and cash equivalents								10,292	6,945
Restricted cash	[1]							1,088	494
Parent company
Operating activities
Net cash provided by operating activities								511	879	1,733
Investing activities
Proceeds from sales of finance receivables and loans initially held-for-investment								6	1	64
Originations and repayments of finance receivables and loans held-for-investment and other, net								(89)	(37)	(7)
Net change in loans — intercompany								(51)	(290)	(65)
Proceeds from sales of equity securities								0	5	1
Capital contributions to subsidiaries								(4)	(8)	0
Returns of contributed capital								0	1	52
Net change in nonmarketable equity investments								0	(2)	8
Other, net								(27)	(10)	(27)
Net cash provided by (used in) investing activities								(165)	(340)	26
Financing activities
Proceeds from issuance of long-term debt								2,050	2,410	1,655
Repayments of long-term debt								(1,482)	(2,087)	(1,088)
Net change in debt — intercompany								274	227	(496)
Repurchases of common stock								(38)	(33)	(1,650)
Common stock dividends paid								(372)	(368)	(384)
Preferred stock dividends paid								(110)	(110)	(110)
Net cash (used in) provided by financing activities								322	39	(2,073)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net increase (decrease) in cash and cash equivalents and restricted cash								668	578	(314)
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash at beginning of year		$ 3,944	$ 3,366	$ 3,944	$ 3,366	$ 3,944	$ 3,366	3,944	3,366	3,680
Cash and cash equivalents and restricted cash at December 31,								4,612	3,944	$ 3,366
Restricted Cash [Abstract]
Cash and cash equivalents								4,579	3,911
Restricted cash								$ 33	$ 33

[1] Refer to Note 13 for additional details describing the nature of restricted cash and cash equivalent balances.