Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) segment	Mar. 31, 2021 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment	3
Summary of Operations
Net interest income	$ 165	$ 189
Provision (benefit) for credit losses	(4)	(28)
Net interest income after provision for credit losses	169	217
Net gain on loan sales	45	227
Loan fees and charges	27	42
Net return on mortgage servicing rights	29	0
Loan administrative (expense) income	33	27
Other noninterest income	26	28
Total noninterest income	160	324
Compensation and benefits	127	144
Commissions	26	62
Loan processing expense	21	21
General, administrative and other	87	120
Total noninterest expense	261	347
Income (loss) before indirect overhead allocations and income taxes	68	194
Indirect overhead allocation (expense) income	0	0
Provision (benefit) for income taxes	15	45
Net income	53	149
Average balances
Loans held-for-sale	4,833	7,464
Loans with government guarantees	1,402	2,502
Loans held-for-investment	12,384	14,915
Total assets	24,161	30,065
Deposits	18,089	20,043
Other
Summary of Operations
Net interest income	(16)	(27)
Provision (benefit) for credit losses	(29)	(12)
Net interest income after provision for credit losses	13	(15)
Net gain on loan sales	0	0
Loan fees and charges	0	0
Net return on mortgage servicing rights	0	0
Loan administrative (expense) income	(3)	(3)
Other noninterest income	7	7
Total noninterest income	4	4
Compensation and benefits	38	43
Commissions	0	0
Loan processing expense	1	1
General, administrative and other	37	51
Total noninterest expense	76	95
Income (loss) before indirect overhead allocations and income taxes	(59)	(106)
Indirect overhead allocation (expense) income	31	35
Provision (benefit) for income taxes	(4)	(10)
Net income	(24)	(61)
Average balances
Loans held-for-sale	0	0
Loans with government guarantees	0	0
Loans held-for-investment	0	30
Total assets	3,973	3,492
Deposits	1,025	1,067
Intersegment Eliminations
Summary of Operations
Intersegment revenue (expense)	(40)	(24)
Community Banking | Operating Segments
Summary of Operations
Net interest income	122	156
Provision (benefit) for credit losses	22	(14)
Net interest income after provision for credit losses	100	170
Net gain on loan sales	0	0
Loan fees and charges	0	0
Net return on mortgage servicing rights	0	0
Loan administrative (expense) income	0	0
Other noninterest income	18	18
Total noninterest income	18	18
Compensation and benefits	28	31
Commissions	1	1
Loan processing expense	2	1
General, administrative and other	18	25
Total noninterest expense	49	58
Income (loss) before indirect overhead allocations and income taxes	69	130
Indirect overhead allocation (expense) income	(10)	(10)
Provision (benefit) for income taxes	12	25
Net income	47	95
Average balances
Loans held-for-sale	18	0
Loans with government guarantees	0	0
Loans held-for-investment	10,942	12,806
Total assets	11,326	13,168
Deposits	12,006	11,804
Community Banking | Intersegment Eliminations
Summary of Operations
Intersegment revenue (expense)	22	14
Mortgage Originations | Operating Segments
Summary of Operations
Net interest income	56	56
Provision (benefit) for credit losses	3	(2)
Net interest income after provision for credit losses	53	58
Net gain on loan sales	45	227
Loan fees and charges	6	24
Net return on mortgage servicing rights	29	0
Loan administrative (expense) income	(7)	(10)
Other noninterest income	1	3
Total noninterest income	74	244
Compensation and benefits	45	54
Commissions	25	61
Loan processing expense	9	11
General, administrative and other	11	22
Total noninterest expense	90	148
Income (loss) before indirect overhead allocations and income taxes	37	154
Indirect overhead allocation (expense) income	(15)	(19)
Provision (benefit) for income taxes	4	28
Net income	18	107
Average balances
Loans held-for-sale	4,815	7,464
Loans with government guarantees	1,404	2,502
Loans held-for-investment	1,442	2,079
Total assets	8,695	13,015
Deposits	42	15
Mortgage Originations | Intersegment Eliminations
Summary of Operations
Intersegment revenue (expense)	9	(2)
Mortgage Servicing | Operating Segments
Summary of Operations
Net interest income	3	4
Provision (benefit) for credit losses	0	0
Net interest income after provision for credit losses	3	4
Net gain on loan sales	0	0
Loan fees and charges	21	18
Net return on mortgage servicing rights	0	0
Loan administrative (expense) income	43	40
Other noninterest income	0	0
Total noninterest income	64	58
Compensation and benefits	16	16
Commissions	0	0
Loan processing expense	9	8
General, administrative and other	21	22
Total noninterest expense	46	46
Income (loss) before indirect overhead allocations and income taxes	21	16
Indirect overhead allocation (expense) income	(6)	(6)
Provision (benefit) for income taxes	3	2
Net income	12	8
Average balances
Loans held-for-sale	0	0
Loans with government guarantees	(2)	0
Loans held-for-investment	0	0
Total assets	167	390
Deposits	5,016	7,157
Mortgage Servicing | Intersegment Eliminations
Summary of Operations
Intersegment revenue (expense)	$ 9	$ 12