Loans - Commercial Banking: Risk Profile by Internal Risk Rating (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 251,512	$ 265,809
Commercial Banking
Loans and Leases Receivable Disclosure [Line Items]
2020	7,615
2019	16,642
2018	9,302
2017	5,720
2016	4,557
Prior	11,229
Total Term Loans	55,065
Revolving Loans	22,352
Revolving Loans Converted to Term	73
Total Loans	77,490	$ 74,508
Internal Risk, Percentage		100.00%
Loans under Paycheck Protection Program	231
Commercial Banking \| PCI loans
Loans and Leases Receivable Disclosure [Line Items]
Total Loans		$ 31
Internal Risk, Percentage		0.00%
Commercial Banking \| Noncriticized
Loans and Leases Receivable Disclosure [Line Items]
Total Loans		$ 71,848
Internal Risk, Percentage		96.50%
Commercial Banking \| Criticized \| Criticized performing
Loans and Leases Receivable Disclosure [Line Items]
Total Loans		$ 2,181
Internal Risk, Percentage		2.90%
Commercial Banking \| Criticized \| Criticized nonperforming
Loans and Leases Receivable Disclosure [Line Items]
Total Loans		$ 448
Internal Risk, Percentage		0.60%
Commercial Banking \| Commercial and multifamily real estate
Loans and Leases Receivable Disclosure [Line Items]
2020	2,535
2019	5,664
2018	3,960
2017	2,211
2016	2,437
Prior	7,213
Total Term Loans	24,020
Revolving Loans	6,933
Revolving Loans Converted to Term	0
Total Loans	30,953	$ 30,245
Internal Risk, Percentage		100.00%
Commercial Banking \| Commercial and multifamily real estate \| PCI loans
Loans and Leases Receivable Disclosure [Line Items]
Total Loans		$ 21
Internal Risk, Percentage		0.10%
Commercial Banking \| Commercial and multifamily real estate \| Noncriticized
Loans and Leases Receivable Disclosure [Line Items]
2020	2,466
2019	5,490
2018	3,587
2017	2,000
2016	2,217
Prior	6,635
Total Term Loans	22,395
Revolving Loans	6,878
Revolving Loans Converted to Term	0
Total Loans	29,273	$ 29,625
Internal Risk, Percentage		97.90%
Commercial Banking \| Commercial and multifamily real estate \| Criticized \| Criticized performing
Loans and Leases Receivable Disclosure [Line Items]
2020	69
2019	163
2018	343
2017	211
2016	216
Prior	456
Total Term Loans	1,458
Revolving Loans	55
Revolving Loans Converted to Term	0
Total Loans	1,513	$ 561
Internal Risk, Percentage		1.90%
Commercial Banking \| Commercial and multifamily real estate \| Criticized \| Criticized nonperforming
Loans and Leases Receivable Disclosure [Line Items]
2020	0
2019	11
2018	30
2017	0
2016	4
Prior	122
Total Term Loans	167
Revolving Loans	0
Revolving Loans Converted to Term	0
Total Loans	167	$ 38
Internal Risk, Percentage		0.10%
Commercial Banking \| Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
2020	5,080
2019	10,978
2018	5,342
2017	3,509
2016	2,120
Prior	4,016
Total Term Loans	31,045
Revolving Loans	15,419
Revolving Loans Converted to Term	73
Total Loans	46,537	$ 44,263
Internal Risk, Percentage		100.00%
Commercial Banking \| Commercial and industrial \| PCI loans
Loans and Leases Receivable Disclosure [Line Items]
Total Loans		$ 10
Internal Risk, Percentage		0.00%
Commercial Banking \| Commercial and industrial \| Noncriticized
Loans and Leases Receivable Disclosure [Line Items]
2020	4,879
2019	10,234
2018	4,758
2017	3,078
2016	1,998
Prior	3,814
Total Term Loans	28,761
Revolving Loans	12,774
Revolving Loans Converted to Term	73
Total Loans	41,608	$ 42,223
Internal Risk, Percentage		95.40%
Commercial Banking \| Commercial and industrial \| Criticized \| Criticized performing
Loans and Leases Receivable Disclosure [Line Items]
2020	169
2019	668
2018	524
2017	371
2016	114
Prior	202
Total Term Loans	2,048
Revolving Loans	2,388
Revolving Loans Converted to Term	0
Total Loans	4,436	$ 1,620
Internal Risk, Percentage		3.70%
Commercial Banking \| Commercial and industrial \| Criticized \| Criticized nonperforming
Loans and Leases Receivable Disclosure [Line Items]
2020	32
2019	76
2018	60
2017	60
2016	8
Prior	0
Total Term Loans	236
Revolving Loans	257
Revolving Loans Converted to Term	0
Total Loans	$ 493	$ 410
Internal Risk, Percentage		0.90%

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