Loans Held-for-Investment - Aging Analysis of Past Due and Current Loans (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Loans, Aging [Abstract]
Total Past Due	$ 55	$ 40
Current	13,740	12,089
Total LHFI	13,795	12,129
Loans greater than 90 days past due accounted for under the fair value option	4
30-59 Days Past Due
Loans, Aging [Abstract]
Total Past Due	21	9
60-89 Days Past Due
Loans, Aging [Abstract]
Total Past Due	5	5
90 Days or Greater Past Due
Loans, Aging [Abstract]
Total Past Due	29	26
Consumer loans
Loans, Aging [Abstract]
Total Past Due	48	40
Current	4,802	4,867
Total LHFI	4,850	4,907
Consumer loans | Residential first mortgage loans
Loans, Aging [Abstract]
Total Past Due	35	30
Current	2,929	3,124
Total LHFI	2,964	3,154
Consumer loans | Home equity
Loans, Aging [Abstract]
Total Past Due	6	5
Current	1,022	1,019
Total LHFI	1,028	1,024
Consumer loans | Other
Loans, Aging [Abstract]
Total Past Due	7	5
Current	851	724
Total LHFI	858	729
Consumer loans | 30-59 Days Past Due
Loans, Aging [Abstract]
Total Past Due	14	9
Consumer loans | 30-59 Days Past Due | Residential first mortgage loans
Loans, Aging [Abstract]
Total Past Due	8	5
Consumer loans | 30-59 Days Past Due | Home equity
Loans, Aging [Abstract]
Total Past Due	2	1
Consumer loans | 30-59 Days Past Due | Other
Loans, Aging [Abstract]
Total Past Due	4	3
Consumer loans | 60-89 Days Past Due
Loans, Aging [Abstract]
Total Past Due	5	5
Consumer loans | 60-89 Days Past Due | Residential first mortgage loans
Loans, Aging [Abstract]
Total Past Due	3	4
Consumer loans | 60-89 Days Past Due | Home equity
Loans, Aging [Abstract]
Total Past Due	1	0
Consumer loans | 60-89 Days Past Due | Other
Loans, Aging [Abstract]
Total Past Due	1	1
Consumer loans | 90 Days or Greater Past Due
Loans, Aging [Abstract]
Total Past Due	29	26
Consumer loans | 90 Days or Greater Past Due | Residential first mortgage loans
Loans, Aging [Abstract]
Total Past Due	24	21
Consumer loans | 90 Days or Greater Past Due | Home equity
Loans, Aging [Abstract]
Total Past Due	3	4
Consumer loans | 90 Days or Greater Past Due | Other
Loans, Aging [Abstract]
Total Past Due	2	1
Commercial loans
Loans, Aging [Abstract]
Total Past Due	7	0
Current	8,938	7,222
Total LHFI	8,945	7,222
Commercial loans | Commercial real estate
Loans, Aging [Abstract]
Total Past Due	6	0
Current	3,086	2,828
Total LHFI	3,092	2,828
Commercial loans | Commercial and industrial
Loans, Aging [Abstract]
Total Past Due	1	0
Current	1,879	1,634
Total LHFI	1,880	1,634
Commercial loans | Warehouse lending
Loans, Aging [Abstract]
Total Past Due	0	0
Current	3,973	2,760
Total LHFI	3,973	2,760
Commercial loans | 30-59 Days Past Due
Loans, Aging [Abstract]
Total Past Due	7	0
Commercial loans | 30-59 Days Past Due | Commercial real estate
Loans, Aging [Abstract]
Total Past Due	6	0
Commercial loans | 30-59 Days Past Due | Commercial and industrial
Loans, Aging [Abstract]
Total Past Due	1	0
Commercial loans | 30-59 Days Past Due | Warehouse lending
Loans, Aging [Abstract]
Total Past Due	0	0
Commercial loans | 60-89 Days Past Due
Loans, Aging [Abstract]
Total Past Due	0	0
Commercial loans | 60-89 Days Past Due | Commercial real estate
Loans, Aging [Abstract]
Total Past Due	0	0
Commercial loans | 60-89 Days Past Due | Commercial and industrial
Loans, Aging [Abstract]
Total Past Due	0	0
Commercial loans | 60-89 Days Past Due | Warehouse lending
Loans, Aging [Abstract]
Total Past Due	0	0
Commercial loans | 90 Days or Greater Past Due
Loans, Aging [Abstract]
Total Past Due	0	0
Commercial loans | 90 Days or Greater Past Due | Commercial real estate
Loans, Aging [Abstract]
Total Past Due	0	0
Commercial loans | 90 Days or Greater Past Due | Commercial and industrial
Loans, Aging [Abstract]
Total Past Due	0	0
Commercial loans | 90 Days or Greater Past Due | Warehouse lending
Loans, Aging [Abstract]
Total Past Due	$ 0	$ 0