Fair Value Measurement - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Financial assets:
Loans Held-for-sale, Fair Value Disclosure	$ 542	$ 191
Level 1
Financial assets:
Cash and cash equivalents	3,360	5,193
Restricted cash for securitization investors	452	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	38,236	25,663
Restricted cash for securitization investors	0	0
Net loans held for investment	0	0
Loans Held-for-sale, Fair Value Disclosure	669	11
Interest receivable	2,297	2,104
Other investments	1,326	1,326
Financial liabilities:
Deposits with defined maturities	77,924	45,531
Securitized debt obligations	17,811	16,918
Senior and subordinated notes	31,334	30,744
Federal funds purchased and securities loaned or sold under agreements to repurchase	649	883
Interest payable	637	527
Level 3
Financial assets:
Cash and cash equivalents	0	0
Restricted cash for securitization investors	0	0
Net loans held for investment	299,206	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	41,596	30,856
Restricted cash for securitization investors	452	400
Net loans held for investment	296,677	299,091
Loans Held-for-sale, Fair Value Disclosure	669	11
Interest receivable	2,297	2,104
Other investments	1,326	1,326
Financial liabilities:
Deposits with defined maturities	78,336	45,858
Securitized debt obligations	17,861	16,973
Senior and subordinated notes	31,627	30,826
Federal funds purchased and securities loaned or sold under agreements to repurchase	649	883
Interest payable	637	527
Estimated Fair Value
Financial assets:
Cash and cash equivalents	41,596	30,856
Restricted cash for securitization investors	452	400
Net loans held for investment	299,206	302,920
Loans Held-for-sale, Fair Value Disclosure	669	11
Interest receivable	2,297	2,104
Other investments	1,326	1,326
Financial liabilities:
Deposits with defined maturities	77,924	45,531
Securitized debt obligations	17,811	16,918
Senior and subordinated notes	31,334	30,744
Federal funds purchased and securities loaned or sold under agreements to repurchase	649	883
Interest payable	$ 637	$ 527