Loans Held-for-Investment - Loan Quality Indicators (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	$ 14,052	$ 16,227
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	432	662
Year Two	524	901
Year Three	657	396
Year Four	286	301
Year Five	187	255
Prior	547	481
Revolving Loans Amortized Cost Basis	944	1,043
Revolving Loans Converted to Term Loans Amortized Cost Basis	50	70
Total	3,627	4,109	$ 4,895
Total loans	3,644	4,126
Consumer loans | Residential first mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,794	2,266
Consumer loans | Residential first mortgage loans | Debt-to-Value Ratio, Greater than 90
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	70	84
Year Two	82	260
Year Three	199	123
Year Four	79	35
Year Five	23	3
Prior	20	19
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	473	524
Consumer loans | Residential first mortgage loans | Debt-to-Value Ratio, 71-90
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	74	169
Year Two	110	180
Year Three	93	66
Year Four	40	99
Year Five	56	72
Prior	240	238
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	613	824
Consumer loans | Residential first mortgage loans | Debt-to-Vale Ratio, 55-70
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	38	83
Year Two	41	60
Year Three	41	22
Year Four	14	82
Year Five	55	96
Prior	162	122
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	351	465
Consumer loans | Residential first mortgage loans | Debt-to-Value Ratio, Less than 55
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	20	26
Year Two	23	48
Year Three	32	26
Year Four	23	76
Year Five	46	81
Prior	100	73
Revolving Loans Amortized Cost Basis	89	93
Revolving Loans Converted to Term Loans Amortized Cost Basis	8	15
Total	341	438
Consumer loans | Residential first mortgage loans | FICO Score, Greater than 750
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	90	195
Year Two	136	272
Year Three	161	118
Year Four	67	193
Year Five	113	181
Prior	289	231
Revolving Loans Amortized Cost Basis	55	55
Revolving Loans Converted to Term Loans Amortized Cost Basis	1	6
Total	912	1,251
Consumer loans | Residential first mortgage loans | FICO Score, 700 to 750
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	64	119
Year Two	70	180
Year Three	118	90
Year Four	62	85
Year Five	56	64
Prior	149	130
Revolving Loans Amortized Cost Basis	24	25
Revolving Loans Converted to Term Loans Amortized Cost Basis	4	7
Total	547	700
Consumer loans | Residential first mortgage loans | FICO Score, Less than 700
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	48	48
Year Two	50	96
Year Three	86	29
Year Four	27	14
Year Five	11	7
Prior	84	91
Revolving Loans Amortized Cost Basis	10	13
Revolving Loans Converted to Term Loans Amortized Cost Basis	3	2
Total	319	300
Consumer loans | Residential first mortgage loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	202	362
Year Two	256	544
Year Three	358	231
Year Four	150	289
Year Five	177	252
Prior	497	420
Revolving Loans Amortized Cost Basis	88	92
Revolving Loans Converted to Term Loans Amortized Cost Basis	7	15
Total	1,735	2,205	3,107
Consumer loans | Residential first mortgage loans | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	1
Year Three	1	1
Year Four	0	1
Year Five	1	0
Prior	2	17
Revolving Loans Amortized Cost Basis	1	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	5	21	23
Consumer loans | Residential first mortgage loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	3
Year Three	6	5
Year Four	6	2
Year Five	2	0
Prior	23	15
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	1	0
Total	38	25	15
Consumer loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	717	856
Consumer loans | Home equity | Debt-to-Value Ratio, Greater than 90
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	1
Year Five	1	1
Prior	9	10
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	10	12
Consumer loans | Home equity | Debt-to-Value Ratio, 71-90
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2	5
Year Two	3	24
Year Three	16	10
Year Four	6	4
Year Five	3	1
Prior	8	9
Revolving Loans Amortized Cost Basis	451	548
Revolving Loans Converted to Term Loans Amortized Cost Basis	27	33
Total	516	634
Consumer loans | Home equity | Debt-to-Value Ratio, Less than or Equal to 70
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	1	2
Year Two	2	7
Year Three	5	3
Year Four	2	1
Year Five	1	0
Prior	3	4
Revolving Loans Amortized Cost Basis	165	175
Revolving Loans Converted to Term Loans Amortized Cost Basis	11	16
Total	190	208
Consumer loans | Home equity | FICO Score, Greater than 750
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3	2
Year Two	2	9
Year Three	6	6
Year Four	3	2
Year Five	2	1
Prior	5	7
Revolving Loans Amortized Cost Basis	286	324
Revolving Loans Converted to Term Loans Amortized Cost Basis	6	13
Total	313	364
Consumer loans | Home equity | FICO Score, 700 to 750
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	3
Year Two	2	12
Year Three	8	4
Year Four	3	3
Year Five	2	1
Prior	8	8
Revolving Loans Amortized Cost Basis	244	289
Revolving Loans Converted to Term Loans Amortized Cost Basis	17	20
Total	284	340
Consumer loans | Home equity | FICO Score, Less than 700
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	2
Year Two	1	10
Year Three	7	3
Year Four	2	1
Year Five	1	0
Prior	7	8
Revolving Loans Amortized Cost Basis	86	110
Revolving Loans Converted to Term Loans Amortized Cost Basis	15	16
Total	119	150
Consumer loans | Home equity | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	3	7
Year Two	5	31
Year Three	21	13
Year Four	8	6
Year Five	5	2
Prior	18	11
Revolving Loans Amortized Cost Basis	613	720
Revolving Loans Converted to Term Loans Amortized Cost Basis	36	48
Total	709	838	1,002
Consumer loans | Home equity | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	0	11
Revolving Loans Amortized Cost Basis	1	2
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	1	13	16
Consumer loans | Home equity | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	2	1
Revolving Loans Amortized Cost Basis	2	1
Revolving Loans Converted to Term Loans Amortized Cost Basis	2	1
Total	6	3	3
Consumer loans | Other consumer | FICO Score, Greater than 750
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	156	209
Year Two	188	205
Year Three	170	80
Year Four	66	2
Year Five	1	1
Prior	3	5
Revolving Loans Amortized Cost Basis	227	213
Revolving Loans Converted to Term Loans Amortized Cost Basis	3	6
Total	814	721
Consumer loans | Other consumer | FICO Score, 700 to 750
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	70	79
Year Two	71	107
Year Three	92	55
Year Four	47	1
Year Five	1	0
Prior	1	1
Revolving Loans Amortized Cost Basis	7	9
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	289	252
Consumer loans | Other consumer | FICO Score, Less than 700
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	1	5
Year Two	4	10
Year Three	9	11
Year Four	9	0
Year Five	0	0
Prior	1	0
Revolving Loans Amortized Cost Basis	5	5
Revolving Loans Converted to Term Loans Amortized Cost Basis	1	0
Total	30	31
Consumer loans | Other consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	227	292
Year Two	262	321
Year Three	270	145
Year Four	121	3
Year Five	2	1
Prior	5	6
Revolving Loans Amortized Cost Basis	239	227
Revolving Loans Converted to Term Loans Amortized Cost Basis	4	5
Total	1,130	1,000	727
Consumer loans | Other consumer | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	1
Total	0	1	1
Consumer loans | Other consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	1
Year Two	1	1
Year Three	1	1
Year Four	1	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3	3	1
Consumer loans | Residential first mortgage and home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	205	369
Year Two	261	579
Year Three	386	250
Year Four	164	298
Year Five	185	254
Prior	542	475
Revolving Loans Amortized Cost Basis	705	816
Revolving Loans Converted to Term Loans Amortized Cost Basis	46	64
Total	2,494	3,105
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	6,095	8,376
Year Two	388	1,508
Year Three	871	711
Year Four	514	701
Year Five	447	400
Prior	535	386
Revolving Loans Amortized Cost Basis	1,558	19
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	10,408	12,101	7,222
Commercial loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	3,169	3,061
Commercial loans | Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	182	347
Year Two	292	993
Year Three	644	439
Year Four	377	438
Year Five	250	308
Prior	454	280
Revolving Loans Amortized Cost Basis	749	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	2,948	2,805	2,794
Commercial loans | Commercial real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	21
Year Two	4	19
Year Three	9	35
Year Four	27	51
Year Five	94	21
Prior	60	19
Revolving Loans Amortized Cost Basis	9	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	203	166	24
Commercial loans | Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	5
Year Two	0	1
Year Three	1	16
Year Four	1	0
Year Five	0	17
Prior	6	14
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	8	53	5
Commercial loans | Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	11
Year Three	2	1
Year Four	0	25
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	8	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	10	37	5
Commercial loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	1,376	1,382
Commercial loans | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	49	319
Year Two	90	425
Year Three	180	163
Year Four	85	149
Year Five	98	54
Prior	15	71
Revolving Loans Amortized Cost Basis	710	19
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	1,227	1,200	1,533
Commercial loans | Commercial and industrial | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	3
Year Two	1	48
Year Three	10	28
Year Four	5	25
Year Five	0	0
Prior	0	2
Revolving Loans Amortized Cost Basis	38	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	54	106	72
Commercial loans | Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	1
Year Two	1	0
Year Three	17	14
Year Four	9	9
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	18	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	45	24	24
Commercial loans | Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	1	22
Year Two	0	11
Year Three	8	15
Year Four	10	4
Year Five	5	0
Prior	0	0
Revolving Loans Amortized Cost Basis	26	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	50	52	5
Commercial loans | Warehouse loan commitments | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	5,718	7,398
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	5,718	7,398	2,556
Commercial loans | Warehouse loan commitments | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	145	260
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	145	260	189
Commercial loans | Warehouse loan commitments | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	0	0	15
Commercial loans | Warehouse loan commitments | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	0
Year Two	0	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total loans	$ 0	$ 0	$ 0