Loans Held-for-Investment - Changes in ALLL by Class of Loan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for Loan Losses
Beginning balance	$ 252	$ 107	$ 128
Provision (benefit)	(101)	131	18
Charge-offs	(19)	(15)	(43)
Recoveries	22	6	4
Ending allowance balance	154	252	$ 107
Accounting Standards Update [Extensible List]			Accounting Standards Update 2016-13 [Member]
Impact of ASC 326 Adoption
Allowance for Loan Losses
Beginning balance		23
Ending allowance balance			$ 23
Accounting Standards Update [Extensible List]			Accounting Standards Update 2016-13 [Member]
Consumer loans | Residential first mortgage
Allowance for Loan Losses
Beginning balance	49	22	$ 38
Provision (benefit)	(6)	8	(14)
Charge-offs	(5)	(6)	(3)
Recoveries	2	0	1
Ending allowance balance	40	49	22
Consumer loans | Residential first mortgage | Impact of ASC 326 Adoption
Allowance for Loan Losses
Beginning balance		25
Ending allowance balance			25
Consumer loans | Home equity
Allowance for Loan Losses
Beginning balance	25	14	15
Provision (benefit)	(12)	(2)	(1)
Charge-offs	(1)	(3)	(2)
Recoveries	2	4	2
Ending allowance balance	14	25	14
Consumer loans | Home equity | Impact of ASC 326 Adoption
Allowance for Loan Losses
Beginning balance		12
Ending allowance balance			12
Consumer loans | Other
Allowance for Loan Losses
Beginning balance	39	6	3
Provision (benefit)	(1)	26	10
Charge-offs	(4)	(5)	(7)
Recoveries	2	2	0
Ending allowance balance	36	39	6
Consumer loans | Other | Impact of ASC 326 Adoption
Allowance for Loan Losses
Beginning balance		10
Ending allowance balance			10
Commercial loans | Commercial real estate
Allowance for Loan Losses
Beginning balance	84	38	48
Provision (benefit)	(56)	60	(10)
Charge-offs	0	0	0
Recoveries	0	0	0
Ending allowance balance	28	84	38
Commercial loans | Commercial real estate | Impact of ASC 326 Adoption
Allowance for Loan Losses
Beginning balance		(14)
Ending allowance balance			(14)
Commercial loans | Commercial and industrial
Allowance for Loan Losses
Beginning balance	51	22	18
Provision (benefit)	(26)	36	34
Charge-offs	(9)	(1)	(31)
Recoveries	16	0	1
Ending allowance balance	32	51	22
Commercial loans | Commercial and industrial | Impact of ASC 326 Adoption
Allowance for Loan Losses
Beginning balance		(6)
Ending allowance balance			(6)
Commercial loans | Warehouse lending
Allowance for Loan Losses
Beginning balance	4	5	6
Provision (benefit)	0	3	(1)
Charge-offs	0	0	0
Recoveries	0	0	0
Ending allowance balance	$ 4	4	5
Commercial loans | Warehouse lending | Impact of ASC 326 Adoption
Allowance for Loan Losses
Beginning balance		$ (4)
Ending allowance balance			$ (4)