Segment Information -Financial Information by Business Segment (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment			3
Summary of Operations
Net interest income	$ 219	$ 195	$ 577	$ 566
Provision (benefit) for credit losses	5	(23)	(8)	(95)
Net interest income after benefit for credit losses	214	218	585	661
Net gain on loan sales	32	169	104	564
Loan fees and charges	20	33	76	112
Net return on mortgage servicing rights	26	9	77	4
Loan administrative (expense) income	18	31	84	85
Other noninterest income (expense)	18	24	64	77
Total noninterest income	114	266	405	842
Compensation and benefits	113	130	362	396
Commissions	15	44	63	156
Loan processing expense	21	22	65	65
General, administrative and other	87	90	263	305
Total noninterest expense	236	286	753	922
Income (loss) before indirect overhead allocations and income taxes	92	198	237	581
Indirect overhead allocation (expense) income	0	0	0	0
Provision for income taxes	19	46	51	133
Net income	73	152	186	448
Intersegment revenue (expense)	0	0	0	0
Average balances
Loans held-for-sale	2,976	7,839	3,787	7,403
Loans with government guarantees	1,275	2,046	1,279	2,295
Loans held-for-investment	14,640	13,540	13,462	14,043
Total assets	25,148	28,047	24,397	28,701
Deposits	17,216	19,686	17,595	19,598
Other
Summary of Operations
Net interest income	31	(30)	22	(85)
Provision (benefit) for credit losses	(10)	(29)	(55)	(83)
Net interest income after benefit for credit losses	41	(1)	77	(2)
Net gain on loan sales	0	0	0	0
Loan fees and charges	0	0	0	(1)
Net return on mortgage servicing rights	0	0	0	0
Loan administrative (expense) income	(17)	(2)	(23)	(8)
Other noninterest income (expense)	6	5	19	20
Total noninterest income	(11)	3	(4)	11
Compensation and benefits	37	42	114	123
Commissions	0	0	0	(1)
Loan processing expense	1	1	3	3
General, administrative and other	16	31	81	128
Total noninterest expense	54	74	198	253
Income (loss) before indirect overhead allocations and income taxes	(24)	(72)	(125)	(244)
Indirect overhead allocation (expense) income	30	25	96	90
Provision for income taxes	1	(6)	1	(22)
Net income	5	(41)	(30)	(132)
Average balances
Loans held-for-sale	0	0	0	0
Loans with government guarantees	0	0	1	(1)
Loans held-for-investment	(3)	11	(2)	22
Total assets	4,209	3,384	4,051	3,475
Deposits	835	1,281	935	1,175
Intersegment Eliminations
Summary of Operations
Intersegment revenue (expense)	(21)	(44)	(90)	(123)
Community Banking | Operating Segments
Summary of Operations
Net interest income	140	149	398	454
Provision (benefit) for credit losses	13	8	48	(5)
Net interest income after benefit for credit losses	127	141	350	459
Net gain on loan sales	0	0	0	0
Loan fees and charges	1	0	1	1
Net return on mortgage servicing rights	0	0	0	0
Loan administrative (expense) income	(1)	0	(2)	(1)
Other noninterest income (expense)	15	16	52	49
Total noninterest income	15	16	51	49
Compensation and benefits	27	24	83	75
Commissions	1	1	2	2
Loan processing expense	1	1	4	4
General, administrative and other	33	14	85	46
Total noninterest expense	62	40	174	127
Income (loss) before indirect overhead allocations and income taxes	80	117	227	381
Indirect overhead allocation (expense) income	(10)	(7)	(32)	(26)
Provision for income taxes	14	23	37	75
Net income	56	87	158	280
Average balances
Loans held-for-sale	0	20	8	14
Loans with government guarantees	0	0	0	0
Loans held-for-investment	11,935	11,846	11,488	12,156
Total assets	12,247	12,224	11,849	12,518
Deposits	11,514	12,116	11,753	11,872
Community Banking | Intersegment Eliminations
Summary of Operations
Intersegment revenue (expense)	9	34	45	93
Mortgage Originations | Operating Segments
Summary of Operations
Net interest income	42	72	144	186
Provision (benefit) for credit losses	2	(2)	(1)	(7)
Net interest income after benefit for credit losses	40	74	145	193
Net gain on loan sales	32	169	104	564
Loan fees and charges	5	13	18	55
Net return on mortgage servicing rights	26	9	77	4
Loan administrative (expense) income	(7)	(7)	(21)	(26)
Other noninterest income (expense)	(3)	3	(7)	8
Total noninterest income	53	187	171	605
Compensation and benefits	32	48	114	151
Commissions	14	43	61	155
Loan processing expense	9	11	27	34
General, administrative and other	16	23	31	65
Total noninterest expense	71	125	233	405
Income (loss) before indirect overhead allocations and income taxes	22	136	83	393
Indirect overhead allocation (expense) income	(13)	(14)	(44)	(50)
Provision for income taxes	2	26	6	72
Net income	7	96	33	271
Average balances
Loans held-for-sale	2,976	7,819	3,779	7,389
Loans with government guarantees	1,275	2,046	1,279	2,296
Loans held-for-investment	2,708	1,683	1,976	1,865
Total assets	8,622	12,356	8,374	12,462
Deposits	34	40	37	26
Mortgage Originations | Intersegment Eliminations
Summary of Operations
Intersegment revenue (expense)	0	0	14	(3)
Mortgage Servicing | Operating Segments
Summary of Operations
Net interest income	6	4	13	11
Provision (benefit) for credit losses	0	0	0	0
Net interest income after benefit for credit losses	6	4	13	11
Net gain on loan sales	0	0	0	0
Loan fees and charges	14	20	57	57
Net return on mortgage servicing rights	0	0	0	0
Loan administrative (expense) income	43	40	130	120
Other noninterest income (expense)	0	0	0	0
Total noninterest income	57	60	187	177
Compensation and benefits	17	16	51	47
Commissions	0	0	0	0
Loan processing expense	10	9	31	24
General, administrative and other	22	22	66	66
Total noninterest expense	49	47	148	137
Income (loss) before indirect overhead allocations and income taxes	14	17	52	51
Indirect overhead allocation (expense) income	(7)	(4)	(20)	(14)
Provision for income taxes	2	3	7	8
Net income	5	10	25	29
Average balances
Loans held-for-sale	0	0	0	0
Loans with government guarantees	0	0	(1)	0
Loans held-for-investment	0	0	0	0
Total assets	70	83	123	246
Deposits	4,833	6,249	4,870	6,525
Mortgage Servicing | Intersegment Eliminations
Summary of Operations
Intersegment revenue (expense)	$ 12	$ 10	$ 31	$ 33