Loans Held-for-Investment - Changes in ALLL by Class of Loan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Loan Losses
Beginning balance ALLL	$ 128,000,000	$ 140,000,000	$ 142,000,000
Charge-offs	(43,000,000)	(8,000,000)	(14,000,000)
Recoveries	4,000,000	4,000,000	6,000,000
Provision (benefit)	18,000,000	(8,000,000)	6,000,000
Ending balance ALLL	107,000,000	128,000,000	140,000,000
Residential first mortgage
Allowance for Loan Losses
Charge-offs	0	0	(1,000,000)
Loans with government guarantees
Allowance for Loan Losses
Charge-offs	(2,000,000)	(2,000,000)	(4,000,000)
Residential first mortgage
Allowance for Loan Losses
Beginning balance ALLL	38,000,000	47,000,000	65,000,000
Charge-offs		(4,000,000)	(8,000,000)
Recoveries		2,000,000	1,000,000
Provision (benefit)		(7,000,000)	(11,000,000)
Ending balance ALLL	22,000,000	38,000,000	47,000,000
Home equity
Allowance for Loan Losses
Beginning balance ALLL	15,000,000	22,000,000	24,000,000
Charge-offs		(2,000,000)	(3,000,000)
Recoveries		1,000,000	2,000,000
Provision (benefit)		(6,000,000)	(1,000,000)
Ending balance ALLL	14,000,000	15,000,000	22,000,000
Other consumer
Allowance for Loan Losses
Beginning balance ALLL	3,000,000	1,000,000	1,000,000
Charge-offs		(2,000,000)	(2,000,000)
Recoveries		1,000,000	1,000,000
Provision (benefit)		3,000,000	1,000,000
Ending balance ALLL	6,000,000	3,000,000	1,000,000
Commercial real estate
Allowance for Loan Losses
Beginning balance ALLL	48,000,000	45,000,000	28,000,000
Charge-offs		0	(1,000,000)
Recoveries		0	1,000,000
Provision (benefit)		3,000,000	17,000,000
Ending balance ALLL	38,000,000	48,000,000	45,000,000
Commercial and industrial
Allowance for Loan Losses
Beginning balance ALLL	18,000,000	19,000,000	17,000,000
Charge-offs		0	0
Recoveries		0	1,000,000
Provision (benefit)		(1,000,000)	1,000,000
Ending balance ALLL	22,000,000	18,000,000	19,000,000
Warehouse lending
Allowance for Loan Losses
Beginning balance ALLL	6,000,000	6,000,000	7,000,000
Charge-offs		0	0
Recoveries		0	0
Provision (benefit)		0	(1,000,000)
Ending balance ALLL	5,000,000	6,000,000	$ 6,000,000
Other consumer | Residential first mortgage
Allowance for Loan Losses
Beginning balance ALLL	38,000,000
Charge-offs	(3,000,000)
Recoveries	1,000,000
Provision (benefit)	(14,000,000)
Ending balance ALLL		38,000,000
Other consumer | Home equity
Allowance for Loan Losses
Beginning balance ALLL	15,000,000
Charge-offs	(2,000,000)
Recoveries	2,000,000
Provision (benefit)	(1,000,000)
Ending balance ALLL		15,000,000
Other consumer | Other consumer
Allowance for Loan Losses
Beginning balance ALLL	3,000,000
Charge-offs	(7,000,000)
Recoveries	0
Provision (benefit)	10,000,000
Ending balance ALLL		3,000,000
Commercial portfolio segment | Commercial real estate
Allowance for Loan Losses
Beginning balance ALLL	48,000,000
Charge-offs	0
Recoveries	0
Provision (benefit)	(10,000,000)
Ending balance ALLL		48,000,000
Commercial portfolio segment | Commercial and industrial
Allowance for Loan Losses
Beginning balance ALLL	18,000,000
Charge-offs	(31,000,000)
Recoveries	1,000,000
Provision (benefit)	34,000,000
Ending balance ALLL		18,000,000
Commercial portfolio segment | Warehouse lending
Allowance for Loan Losses
Beginning balance ALLL	6,000,000
Charge-offs	0
Recoveries	0
Provision (benefit)	$ (1,000,000)
Ending balance ALLL		$ 6,000,000