Asset Quality (Commercial Lending Asset Quality Indicators) (Details) - USD ($) $ in Millions	Sep. 30, 2018		Dec. 31, 2017		Sep. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 223,053	[1]	$ 220,458	[1]	$ 221,109
Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	149,448		147,439		$ 148,527
Total commercial lending [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	113,671		110,527
Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,563		28,978
Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,214		7,934
Pass [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	143,111		141,414
Pass [Member] | Total commercial lending [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	107,854		105,280
Pass [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,194		28,380
Pass [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,063		7,754
Special Mention [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	2,257		2,083
Special Mention [Member] | Total commercial lending [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	2,046		1,858
Special Mention [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	127		148
Special Mention [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	84		77
Substandard [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	4,027		3,868
Substandard [Member] | Total commercial lending [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,722		3,331
Substandard [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	241		435
Substandard [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	64		102
Doubtful [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	53		74
Doubtful [Member] | Total commercial lending [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	49		58
Doubtful [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	1		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 $1.0 billion, Loans of $.8 billion and Other assets of $.2 billion at September 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.