Loans and Related Allowance for Credit Losses (Home Equity and Residential Real Estate Credit Quality Indicators) (Details) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	[1]	$ 290,230	$ 241,928
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		231	3,434
Financing receivable, originated in year one		2,825	2,000
Financing receivable, originated in year two		1,424	590
Financing receivable, originated in year three		428	830
Financing receivable, originated in year four		619	694
Prior		3,636	4,000
Revolving Loans		9,819	8,794
Revolving Loans Converted to Term		5,497	3,746
Total Loans		24,479	24,088
Home equity | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		12
Financing receivable, originated in year one		8
Financing receivable, originated in year two		7
Financing receivable, originated in year three		7
Financing receivable, originated in year four		4
Prior		101
Revolving Loans		2,229
Revolving Loans Converted to Term		2
Total Loans		2,370
Home equity | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		219
Financing receivable, originated in year one		2,817
Financing receivable, originated in year two		1,417
Financing receivable, originated in year three		421
Financing receivable, originated in year four		615
Prior		3,535
Revolving Loans		7,590
Revolving Loans Converted to Term		5,495
Total Loans		22,109
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		12,828	7,996
Financing receivable, originated in year one		9,478	4,158
Financing receivable, originated in year two		3,661	1,172
Financing receivable, originated in year three		1,258	1,942
Financing receivable, originated in year four		1,874	2,069
Prior		9,115	5,223
Total Loans		38,214	22,560
Residential real estate | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		10,072
Financing receivable, originated in year one		5,965
Financing receivable, originated in year two		2,336
Financing receivable, originated in year three		691
Financing receivable, originated in year four		1,247
Prior		5,280
Total Loans		25,591
Residential real estate | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		2,756
Financing receivable, originated in year one		3,513
Financing receivable, originated in year two		1,325
Financing receivable, originated in year three		567
Financing receivable, originated in year four		627
Prior		3,835
Total Loans		12,623
Greater than or equal to 780 | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		129	2,019
Financing receivable, originated in year one		1,756	1,094
Financing receivable, originated in year two		787	311
Financing receivable, originated in year three		221	525
Financing receivable, originated in year four		403	449
Prior		2,237	2,467
Revolving Loans		5,812	5,382
Revolving Loans Converted to Term		2,706	1,480
Total Loans		14,051	13,727
Greater than or equal to 780 | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		7,778	5,425
Financing receivable, originated in year one		6,577	3,099
Financing receivable, originated in year two		2,405	814
Financing receivable, originated in year three		701	1,432
Financing receivable, originated in year four		1,170	1,538
Prior		4,549	2,551
Total Loans		23,180	14,859
720 to 779 | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		69	1,028
Financing receivable, originated in year one		745	558
Financing receivable, originated in year two		385	153
Financing receivable, originated in year three		107	181
Financing receivable, originated in year four		125	145
Prior		712	777
Revolving Loans		2,403	2,137
Revolving Loans Converted to Term		1,405	941
Total Loans		5,951	5,920
720 to 779 | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		3,957	2,268
Financing receivable, originated in year one		1,917	820
Financing receivable, originated in year two		733	220
Financing receivable, originated in year three		250	340
Financing receivable, originated in year four		372	335
Prior		1,670	818
Total Loans		8,899	4,801
660 to 719 | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		24	334
Financing receivable, originated in year one		270	273
Financing receivable, originated in year two		192	86
Financing receivable, originated in year three		65	84
Financing receivable, originated in year four		59	66
Prior		370	402
Revolving Loans		1,140	985
Revolving Loans Converted to Term		741	625
Total Loans		2,861	2,855
660 to 719 | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		498	252
Financing receivable, originated in year one		464	161
Financing receivable, originated in year two		292	76
Financing receivable, originated in year three		145	98
Financing receivable, originated in year four		144	92
Prior		821	475
Total Loans		2,364	1,154
Less than 660 | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		3	52
Financing receivable, originated in year one		52	74
Financing receivable, originated in year two		59	39
Financing receivable, originated in year three		34	39
Financing receivable, originated in year four		31	33
Prior		305	345
Revolving Loans		411	277
Revolving Loans Converted to Term		561	620
Total Loans		1,456	1,479
Less than 660 | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		52	40
Financing receivable, originated in year one		123	48
Financing receivable, originated in year two		92	33
Financing receivable, originated in year three		80	31
Financing receivable, originated in year four		85	41
Prior		805	485
Total Loans		1,237	678
No FICO score available | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		6	1
Financing receivable, originated in year one		2	1
Financing receivable, originated in year two		1	1
Financing receivable, originated in year three		1	1
Financing receivable, originated in year four		1	1
Prior		12	9
Revolving Loans		53	13
Revolving Loans Converted to Term		84	80
Total Loans		160	107
No FICO score available | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		542	4
Financing receivable, originated in year one		382	2
Financing receivable, originated in year two		101	2
Financing receivable, originated in year three		50	3
Financing receivable, originated in year four		63	6
Prior		547	129
Total Loans		1,685	146
Government insured or guaranteed loans | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		1	7
Financing receivable, originated in year one		15	28
Financing receivable, originated in year two		38	27
Financing receivable, originated in year three		32	38
Financing receivable, originated in year four		40	57
Prior		723	765
Total Loans		849	922
Government insured or guaranteed loans | Residential real estate | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in year one		4
Financing receivable, originated in year two		14
Financing receivable, originated in year three		11
Financing receivable, originated in year four		10
Prior		35
Total Loans		74
Government insured or guaranteed loans | Residential real estate | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		1
Financing receivable, originated in year one		11
Financing receivable, originated in year two		24
Financing receivable, originated in year three		21
Financing receivable, originated in year four		30
Prior		688
Total Loans		775
Greater than 100% | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year			8
Financing receivable, originated in year one			44
Financing receivable, originated in year two			18
Financing receivable, originated in year three			15
Financing receivable, originated in year four			9
Prior			88
Revolving Loans			580
Revolving Loans Converted to Term			279
Total Loans			1,041
Greater than 100% | Home equity | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Prior		3
Revolving Loans		68
Total Loans		71
Greater than 100% | Home equity | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		1
Financing receivable, originated in year one		16
Financing receivable, originated in year two		15
Financing receivable, originated in year three		2
Financing receivable, originated in year four		2
Prior		30
Revolving Loans		270
Revolving Loans Converted to Term		91
Total Loans		427
Greater than 100% | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year			3
Financing receivable, originated in year one			52
Financing receivable, originated in year two			26
Financing receivable, originated in year three			42
Financing receivable, originated in year four			41
Prior			160
Total Loans			324
Greater than 100% | Residential real estate | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		13
Financing receivable, originated in year one		23
Financing receivable, originated in year two		2
Financing receivable, originated in year three		2
Financing receivable, originated in year four		4
Prior		18
Total Loans		62
Greater than 100% | Residential real estate | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		1
Financing receivable, originated in year one		9
Financing receivable, originated in year two		12
Financing receivable, originated in year three		2
Financing receivable, originated in year four		4
Prior		71
Total Loans		99
Greater than or equal to 80% to 100% | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year			517
Financing receivable, originated in year one			320
Financing receivable, originated in year two			59
Financing receivable, originated in year three			42
Financing receivable, originated in year four			25
Prior			158
Revolving Loans			1,781
Revolving Loans Converted to Term			591
Total Loans			3,493
Greater than or equal to 80% to 100% | Home equity | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		4
Financing receivable, originated in year one		4
Financing receivable, originated in year two		2
Financing receivable, originated in year three		2
Financing receivable, originated in year four		1
Prior		14
Revolving Loans		567
Revolving Loans Converted to Term		1
Total Loans		595
Greater than or equal to 80% to 100% | Home equity | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		17
Financing receivable, originated in year one		97
Financing receivable, originated in year two		87
Financing receivable, originated in year three		18
Financing receivable, originated in year four		13
Prior		78
Revolving Loans		847
Revolving Loans Converted to Term		570
Total Loans		1,727
Greater than or equal to 80% to 100% | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year			495
Financing receivable, originated in year one			422
Financing receivable, originated in year two			127
Financing receivable, originated in year three			156
Financing receivable, originated in year four			124
Prior			307
Total Loans			1,631
Greater than or equal to 80% to 100% | Residential real estate | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		847
Financing receivable, originated in year one		1,225
Financing receivable, originated in year two		488
Financing receivable, originated in year three		241
Financing receivable, originated in year four		243
Prior		534
Total Loans		3,578
Greater than or equal to 80% to 100% | Residential real estate | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		711
Financing receivable, originated in year one		143
Financing receivable, originated in year two		107
Financing receivable, originated in year three		30
Financing receivable, originated in year four		34
Prior		165
Total Loans		1,190
Less than 80% | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year			2,909
Financing receivable, originated in year one			1,636
Financing receivable, originated in year two			513
Financing receivable, originated in year three			773
Financing receivable, originated in year four			660
Prior			3,754
Revolving Loans			6,433
Revolving Loans Converted to Term			2,876
Total Loans			19,554
Less than 80% | Home equity | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		7
Financing receivable, originated in year one		4
Financing receivable, originated in year two		5
Financing receivable, originated in year three		5
Financing receivable, originated in year four		3
Prior		80
Revolving Loans		1,575
Revolving Loans Converted to Term		1
Total Loans		1,680
Less than 80% | Home equity | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		201
Financing receivable, originated in year one		2,704
Financing receivable, originated in year two		1,315
Financing receivable, originated in year three		401
Financing receivable, originated in year four		600
Prior		3,427
Revolving Loans		6,473
Revolving Loans Converted to Term		4,834
Total Loans		19,955
Less than 80% | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year			7,491
Financing receivable, originated in year one			3,656
Financing receivable, originated in year two			992
Financing receivable, originated in year three			1,706
Financing receivable, originated in year four			1,847
Prior			3,991
Total Loans			$ 19,683
Less than 80% | Residential real estate | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		1,689
Financing receivable, originated in year one		1,941
Financing receivable, originated in year two		728
Financing receivable, originated in year three		287
Financing receivable, originated in year four		369
Prior		3,248
Total Loans		8,262
Less than 80% | Residential real estate | Financial Asset Originated
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		9,359
Financing receivable, originated in year one		5,802
Financing receivable, originated in year two		2,193
Financing receivable, originated in year three		638
Financing receivable, originated in year four		1,179
Prior		4,356
Total Loans		23,527
No LTV ratio available | Home equity | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		1
Prior		4
Revolving Loans		19
Total Loans		24
No LTV ratio available | Residential real estate | Acquired Loans Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, originated in current year		207
Financing receivable, originated in year one		320
Financing receivable, originated in year two		93
Financing receivable, originated in year three		26
Financing receivable, originated in year four		1
Total Loans		$ 647

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $2.0 billion, Loans held for investment of $1.6 billion and Other assets of $0.1 billion at September 30, 2021. Comparable amounts at December 31, 2020 were $1.2 billion, $1.4 billion and $0.1 billion, respectively.