Loans - Commercial Banking: Risk Profile by Internal Risk Rating (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	$ 261,390	$ 251,624
Commercial Banking
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	12,136	14,262
Term loans by vintage year two	11,341	14,181
Term loans by vintage year three	11,562	8,366
Term loans by vintage year four	6,467	4,818
Term loans by vintage year five	3,276	3,990
Term loans by vintage after year five	9,878	9,561
Total term loans	54,660	55,178
Revolving loans	24,493	20,455
Revolving loans converted to term	95	147
Total	79,248	75,780
PPP loans	182	238
Commercial Banking \| Commercial and multifamily real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	3,879	4,111
Term loans by vintage year two	3,596	5,389
Term loans by vintage year three	4,398	3,777
Term loans by vintage year four	2,946	1,798
Term loans by vintage year five	1,171	2,043
Term loans by vintage after year five	6,030	6,312
Total term loans	22,020	23,430
Revolving loans	11,051	7,226
Revolving loans converted to term	25	25
Total	33,096	30,681
Commercial Banking \| Commercial and multifamily real estate \| Noncriticized
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	3,663	3,791
Term loans by vintage year two	3,320	4,932
Term loans by vintage year three	3,984	3,232
Term loans by vintage year four	2,583	1,437
Term loans by vintage year five	924	1,649
Term loans by vintage after year five	4,455	4,904
Total term loans	18,929	19,945
Revolving loans	10,950	7,114
Revolving loans converted to term	0	0
Total	29,879	27,059
Commercial Banking \| Commercial and multifamily real estate \| Criticized \| Criticized performing
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	216	320
Term loans by vintage year two	276	446
Term loans by vintage year three	406	515
Term loans by vintage year four	334	355
Term loans by vintage year five	237	391
Term loans by vintage after year five	1,335	1,258
Total term loans	2,804	3,285
Revolving loans	101	112
Revolving loans converted to term	25	25
Total	2,930	3,422
Commercial Banking \| Commercial and multifamily real estate \| Criticized \| Criticized nonperforming
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	0	0
Term loans by vintage year two	0	11
Term loans by vintage year three	8	30
Term loans by vintage year four	29	6
Term loans by vintage year five	10	3
Term loans by vintage after year five	240	150
Total term loans	287	200
Revolving loans	0	0
Revolving loans converted to term	0	0
Total	287	200
Commercial Banking \| Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	8,257	10,151
Term loans by vintage year two	7,745	8,792
Term loans by vintage year three	7,164	4,589
Term loans by vintage year four	3,521	3,020
Term loans by vintage year five	2,105	1,947
Term loans by vintage after year five	3,848	3,249
Total term loans	32,640	31,748
Revolving loans	13,442	13,229
Revolving loans converted to term	70	122
Total	46,152	45,099
Commercial Banking \| Commercial And Industrial [Member] \| Noncriticized
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	8,064	9,761
Term loans by vintage year two	7,519	7,890
Term loans by vintage year three	6,200	4,043
Term loans by vintage year four	3,219	2,717
Term loans by vintage year five	1,913	1,832
Term loans by vintage after year five	3,677	3,034
Total term loans	30,592	29,277
Revolving loans	12,677	11,548
Revolving loans converted to term	70	80
Total	43,339	40,905
Commercial Banking \| Commercial And Industrial [Member] \| Criticized \| Criticized performing
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	150	316
Term loans by vintage year two	169	794
Term loans by vintage year three	881	521
Term loans by vintage year four	260	252
Term loans by vintage year five	184	106
Term loans by vintage after year five	153	215
Total term loans	1,797	2,204
Revolving loans	702	1,498
Revolving loans converted to term	0	42
Total	2,499	3,744
Commercial Banking \| Commercial And Industrial [Member] \| Criticized \| Criticized nonperforming
Financing Receivable, Allowance for Credit Loss [Line Items]
Term loans by vintage year one	43	74
Term loans by vintage year two	57	108
Term loans by vintage year three	83	25
Term loans by vintage year four	42	51
Term loans by vintage year five	8	9
Term loans by vintage after year five	18	0
Total term loans	251	267
Revolving loans	63	183
Revolving loans converted to term	0	0
Total	$ 314	$ 450

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