Loans Held-for-Investment - Aging Analysis of Past Due and Current Loans (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Loans Past Due [Line Items]
Total loans held-for-investment	$ 15,793	$ 13,408
Loans greater than 90 days past due accounted for under the fair value option	8	9
Interest income recognized (less than)	1	1
Asset pledged as collateral | Notes Payable, Other Payables
Loans Past Due [Line Items]
Total loans held-for-investment	108	108
30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	18	26
60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	16	36
90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	96	94
Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	130	156
Current
Loans Past Due [Line Items]
Total loans held-for-investment	15,663	13,252
Consumer loans
Loans Past Due [Line Items]
Total loans held-for-investment	5,327	3,385
Consumer loans | 30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	16	26
Consumer loans | 60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	7	36
Consumer loans | 90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	94	62
Consumer loans | Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	117	124
Consumer loans | Current
Loans Past Due [Line Items]
Total loans held-for-investment	5,210	3,261
Consumer loans | Residential first mortgage loans
Loans Past Due [Line Items]
Total loans held-for-investment	3,147	1,536
Consumer loans | Residential first mortgage loans | 30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	10	14
Consumer loans | Residential first mortgage loans | 60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	3	34
Consumer loans | Residential first mortgage loans | 90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	82	49
Consumer loans | Residential first mortgage loans | Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	95	97
Consumer loans | Residential first mortgage loans | Current
Loans Past Due [Line Items]
Total loans held-for-investment	3,052	1,439
Consumer loans | Home equity
Loans Past Due [Line Items]
Total loans held-for-investment	769	613
Consumer loans | Home equity | 30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	3	8
Consumer loans | Home equity | 60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	1	1
Consumer loans | Home equity | 90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	8	9
Consumer loans | Home equity | Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	12	18
Consumer loans | Home equity | Current
Loans Past Due [Line Items]
Total loans held-for-investment	757	595
Consumer loans | Other
Loans Past Due [Line Items]
Total loans held-for-investment	1,411	1,236
Consumer loans | Other | 30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	3	4
Consumer loans | Other | 60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	3	1
Consumer loans | Other | 90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	4	4
Consumer loans | Other | Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	10	9
Consumer loans | Other | Current
Loans Past Due [Line Items]
Total loans held-for-investment	1,401	1,227
Commercial loans
Loans Past Due [Line Items]
Total loans held-for-investment	10,466	10,023
Commercial loans | 30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	2	0
Commercial loans | 60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	9	0
Commercial loans | 90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	2	32
Commercial loans | Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	13	32
Commercial loans | Current
Loans Past Due [Line Items]
Total loans held-for-investment	10,453	9,991
Commercial loans | Commercial real estate
Loans Past Due [Line Items]
Total loans held-for-investment	3,721	3,223
Commercial loans | Commercial real estate | 30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	0	0
Commercial loans | Commercial real estate | 60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	0	0
Commercial loans | Commercial real estate | 90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	0	0
Commercial loans | Commercial real estate | Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	0	0
Commercial loans | Commercial real estate | Current
Loans Past Due [Line Items]
Total loans held-for-investment	3,721	3,223
Commercial loans | Commercial and industrial
Loans Past Due [Line Items]
Total loans held-for-investment	3,188	1,826
Commercial loans | Commercial and industrial | 30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	0	0
Commercial loans | Commercial and industrial | 60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	5	0
Commercial loans | Commercial and industrial | 90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	0	32
Commercial loans | Commercial and industrial | Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	5	32
Commercial loans | Commercial and industrial | Current
Loans Past Due [Line Items]
Total loans held-for-investment	3,183	1,794
Commercial loans | Warehouse lending
Loans Past Due [Line Items]
Total loans held-for-investment	3,557	4,974
Commercial loans | Warehouse lending | 30-59 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	2	0
Commercial loans | Warehouse lending | 60-89 Days Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	4	0
Commercial loans | Warehouse lending | 90 Days or Greater Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	2	0
Commercial loans | Warehouse lending | Total Past Due
Loans Past Due [Line Items]
Total loans held-for-investment	8	0
Commercial loans | Warehouse lending | Current
Loans Past Due [Line Items]
Total loans held-for-investment	$ 3,549	$ 4,974