Borrowings - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended
	Mar. 31, 2024	Feb. 29, 2024	Oct. 31, 2023	Jan. 31, 2023	Sep. 30, 2024	Aug. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Asset-backed notes					$ 1,354		$ 474
Short-term borrowings					2,605		5,316
FHLB advances					2,004		5
Senior notes					3,744		3,741
Long-term borrowings					11,583		$ 8,201
Secured Debt
Debt Instrument [Line Items]
Long-term debt term (in years)	2 years
Weighted average interest rate	5.29%
Secured Debt | Third Party Investors
Debt Instrument [Line Items]
Asset-backed notes	$ 511
FHLB of New York
Debt Instrument [Line Items]
FHLB advances		$ 2,000
Variable interest rate of debt instrument		0.25%
Available line of credit					15,800
FRB of New York
Debt Instrument [Line Items]
Available line of credit					$ 23,800
4.874% Asset-Backed Notes | Secured Debt | Subsidiaries
Debt Instrument [Line Items]
Asset-backed notes						$ 650
Long-term debt term (in years)						2 years
Weighted average interest rate						4.87%
5.053% Fixed Rate Senior Notes Due to Mature in January 2034
Debt Instrument [Line Items]
Variable interest rate of debt instrument	2.26%
Senior notes	$ 850
Interest rate of debt instrument	6.082%
Senior notes maturity date				Jan. 31, 2034
4.65% Fixed Rate Senior Notes Due to Mature in January 2026
Debt Instrument [Line Items]
Senior notes maturity date				Jan. 31, 2026
4.70% Fixed Rate Senior Notes Due to Mature in January 2028
Debt Instrument [Line Items]
Senior notes maturity date				Jan. 31, 2028
7.41% Fixed Rate Senior Notes Due to Mature in October 2029
Debt Instrument [Line Items]
Senior notes maturity date			Jan. 31, 2034