Fair Value Measurement - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Financial assets:
Loans Held-for-sale, Fair Value Disclosure	$ 358	$ 191
Level 1
Financial assets:
Cash and cash equivalents	3,347	5,193
Restricted cash for securitization investors	460	400
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
Interest payable	0	0
Level 2
Financial assets:
Cash and cash equivalents	43,166	25,663
Restricted cash for securitization investors	0	0
Net loans held for investment	0	0
Loans Held-for-sale, Fair Value Disclosure	5	11
Interest receivable	2,250	2,104
Other investments	1,327	1,326
Financial liabilities:
Deposits with defined maturities	75,495	45,531
Securitized debt obligations	17,737	16,918
Senior and subordinated notes	29,585	30,744
Federal funds purchased and securities loaned or sold under agreements to repurchase	542	883
Interest payable	621	527
Level 3
Financial assets:
Cash and cash equivalents	0	0
Restricted cash for securitization investors	0	0
Net loans held for investment	300,206	302,920
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
Interest payable	0	0
Carrying Value
Financial assets:
Cash and cash equivalents	46,513	30,856
Restricted cash for securitization investors	460	400
Net loans held for investment	294,518	299,091
Loans Held-for-sale, Fair Value Disclosure	5	11
Interest receivable	2,250	2,104
Other investments	1,327	1,326
Financial liabilities:
Deposits with defined maturities	76,044	45,858
Securitized debt obligations	17,813	16,973
Senior and subordinated notes	30,398	30,826
Federal funds purchased and securities loaned or sold under agreements to repurchase	542	883
Interest payable	621	527
Estimated Fair Value
Financial assets:
Cash and cash equivalents	46,513	30,856
Restricted cash for securitization investors	460	400
Net loans held for investment	300,206	302,920
Loans Held-for-sale, Fair Value Disclosure	5	11
Interest receivable	2,250	2,104
Other investments	1,327	1,326
Financial liabilities:
Deposits with defined maturities	75,495	45,531
Securitized debt obligations	17,737	16,918
Senior and subordinated notes	29,585	30,744
Federal funds purchased and securities loaned or sold under agreements to repurchase	542	883
Interest payable	$ 621	$ 527