Asset Quality (Commercial Lending Asset Quality Indicators) (Details) - USD ($) $ in Millions	Jun. 30, 2018		Dec. 31, 2017		Jun. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 222,855	[1]	$ 220,458	[1]	$ 218,034
Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	149,636		147,439		$ 145,765
Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	113,367		110,527
Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,946		28,978
Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,323		7,934
Pass [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	143,260		141,414
Pass [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	107,584		105,280
Pass [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,523		28,380
Pass [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,153		7,754
Special Mention [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	2,421		2,083
Special Mention [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	2,180		1,858
Special Mention [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	159		148
Special Mention [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	82		77
Substandard [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,882		3,868
Substandard [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,535		3,331
Substandard [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	262		435
Substandard [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	85		102
Doubtful [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	73		74
Doubtful [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	68		58
Doubtful [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	2		15
Doubtful [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 3		$ 1

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.2 billion, Loans of $.8 billion and Other assets of $.2 billion at June 30, 2018 and Loans held for sale of $1.7 billion, Loans of $.9 billion and Other assets of $.3 billion at December 31, 2017.