Fair Value Measurement - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Financial assets:
Loans Held-for-sale, Fair Value Disclosure	$ 928	$ 1,000
Level 1
Financial assets:
Cash and cash equivalents	5,107	4,164
Restricted cash for securitization investors	281	308
Net loans held for investment	0	0
Loans Held-for-sale, Fair Value Disclosure	0	0
Interest receivable	0	0
Other investments	0	0
Financial liabilities:
Deposits with defined maturities	0	0
Securitized debt obligations	0	0
Senior and subordinated notes	0	0
Federal funds purchased and securities loaned or sold under agreements to repurchase	0	0
Other borrowings	0
Interest payable	0	0
Level 2
Financial assets:
Cash and cash equivalents	21,697	17,582
Restricted cash for securitization investors	0	0
Net loans held for investment	0	0
Loans Held-for-sale, Fair Value Disclosure	227	5,091
Interest receivable	1,479	1,460
Other investments	1,492	1,344
Financial liabilities:
Deposits with defined maturities	17,218	18,062
Securitized debt obligations	13,773	15,122
Senior and subordinated notes	27,234	27,842
Federal funds purchased and securities loaned or sold under agreements to repurchase	594	820
Other borrowings	4,000
Interest payable	261	281
Level 3
Financial assets:
Cash and cash equivalents	0	0
Restricted cash for securitization investors	0	0
Net loans held for investment	273,434	270,508
Loans Held-for-sale, Fair Value Disclosure	0	0
Interest receivable	0	0
Other investments	0	0
Financial liabilities:
Deposits with defined maturities	0	0
Securitized debt obligations	0	0
Senior and subordinated notes	0	0
Federal funds purchased and securities loaned or sold under agreements to repurchase	0	0
Other borrowings	0
Interest payable	0	0
Carrying Value
Financial assets:
Cash and cash equivalents	26,804	21,746
Restricted cash for securitization investors	281	308
Net loans held for investment	269,158	265,910
Loans Held-for-sale, Fair Value Disclosure	227	4,862
Interest receivable	1,479	1,460
Other investments	1,492	1,344
Financial liabilities:
Deposits with defined maturities	17,306	17,923
Securitized debt obligations	13,740	14,994
Senior and subordinated notes	26,976	27,219
Federal funds purchased and securities loaned or sold under agreements to repurchase	594	820
Other borrowings	4,000
Interest payable	261	281
Estimated Fair Value
Financial assets:
Cash and cash equivalents	26,804	21,746
Restricted cash for securitization investors	281	308
Net loans held for investment	273,434	270,508
Loans Held-for-sale, Fair Value Disclosure	227	5,091
Interest receivable	1,479	1,460
Other investments	1,492	1,344
Financial liabilities:
Deposits with defined maturities	17,218	18,062
Securitized debt obligations	13,773	15,122
Senior and subordinated notes	27,234	27,842
Federal funds purchased and securities loaned or sold under agreements to repurchase	594	820
Other borrowings	4,000
Interest payable	$ 261	$ 281