Asset Quality (Commercial Lending Asset Quality Indicators) (Details) - USD ($) $ in Millions	Sep. 30, 2017		Dec. 31, 2016		Sep. 30, 2016
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 221,109	[1]	$ 210,833	[1]	$ 210,446
Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	148,527		137,955		$ 138,163
Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	111,317		101,364
Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	29,516		29,010
Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,694		7,581
Pass [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	142,557		132,187
Pass [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	106,168		96,231
Pass [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,874		28,561
Pass [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,515		7,395
Special Mention [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	1,998		1,799
Special Mention [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	1,741		1,612
Special Mention [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	168		98
Special Mention [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	89		89
Substandard [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,884		3,867
Substandard [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,340		3,449
Substandard [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	457		327
Substandard [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	87		91
Doubtful [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	88		102
Doubtful [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	68		72
Doubtful [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	17		24
Doubtful [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 3		$ 6

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.6 billion, Loans of $.8 billion and Other assets of $.3 billion at September 30, 2017 and Loans held for sale of $2.4 billion, Loans of $.9 billion and Other assets of $.5 billion at December 31, 2016.