Fair Value Measurement - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financial assets:
Loans held for sale	$ 1,000	$ 596
Level 1
Financial assets:
Cash and cash equivalents	4,164	4,708
Restricted cash for securitization investors	308	262
Net loans held for investment	0	0
Loans held for sale	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	17,582	35,801
Restricted cash for securitization investors	0	0
Net loans held for investment	0	0
Loans held for sale	5,091	2,214
Interest receivable	1,460	1,471
Other investments	1,344	1,341
Financial liabilities:
Deposits with defined maturities	18,062	33,111
Securitized debt obligations	15,122	12,584
Senior and subordinated notes	27,842	28,282
Federal funds purchased and securities loaned or sold under agreements to repurchase	820	668
Interest payable	281	352
Level 3
Financial assets:
Cash and cash equivalents	0	0
Restricted cash for securitization investors	0	0
Net loans held for investment	270,508	244,701
Loans held for sale	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	21,746	40,509
Restricted cash for securitization investors	308	262
Net loans held for investment	265,910	236,060
Loans held for sale	4,862	2,114
Interest receivable	1,460	1,471
Other investments	1,344	1,341
Financial liabilities:
Deposits with defined maturities	17,923	32,746
Securitized debt obligations	14,994	12,414
Senior and subordinated notes	27,219	27,382
Federal funds purchased and securities loaned or sold under agreements to repurchase	820	668
Interest payable	281	352
Estimated Fair Value
Financial assets:
Cash and cash equivalents	21,746	40,509
Restricted cash for securitization investors	308	262
Net loans held for investment	270,508	244,701
Loans held for sale	5,091	2,214
Interest receivable	1,460	1,471
Other investments	1,344	1,341
Financial liabilities:
Deposits with defined maturities	18,062	33,111
Securitized debt obligations	15,122	12,584
Senior and subordinated notes	27,842	28,282
Federal funds purchased and securities loaned or sold under agreements to repurchase	820	668
Interest payable	$ 281	$ 352