Loans Held-for-Investment - Changes in ALLL by Class of Loan (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Allowance for Loan Losses [Roll Forward]
Beginning balance ALLL	$ 127	$ 139	$ 128	$ 140
Charge-offs	(35)	(2)	(37)	(4)
Recoveries	1	1	2	2
Provision (benefit)	17	(1)	17	(1)
Ending balance ALLL	110	137	110	137
Residential first mortgage
Allowance for Loan Losses [Roll Forward]
Beginning balance ALLL	35	47	38	47
Charge-offs	(1)	0	(2)	(1)
Recoveries	0	0	0	0
Provision (benefit)	(8)	(2)	(10)	(1)
Ending balance ALLL	26	45	26	45
Home equity
Allowance for Loan Losses [Roll Forward]
Beginning balance ALLL	16	21	15	22
Charge-offs	0	(1)	0	(2)
Recoveries	0	1	1	2
Provision (benefit)	0	(2)	0	(3)
Ending balance ALLL	16	19	16	19
Other Consumer
Allowance for Loan Losses [Roll Forward]
Beginning balance ALLL	4	1	3	1
Charge-offs	(3)	(1)	(4)	(1)
Recoveries	1	0	1	0
Provision (benefit)	3	1	5	1
Ending balance ALLL	5	1	5	1
Commercial real estate
Allowance for Loan Losses [Roll Forward]
Beginning balance ALLL	36	44	48	45
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	(1)	1	(13)	0
Ending balance ALLL	35	45	35	45
Commercial and industrial
Allowance for Loan Losses [Roll Forward]
Beginning balance ALLL	30	20	18	19
Charge-offs	(31)	0	(31)	0
Recoveries	0	0	0	0
Provision (benefit)	24	1	36	2
Ending balance ALLL	23	21	23	21
Warehouse lending
Allowance for Loan Losses [Roll Forward]
Beginning balance ALLL	6	6	6	6
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	(1)	0	(1)	0
Ending balance ALLL	$ 5	$ 6	$ 5	$ 6