Asset Quality (Commercial Lending Asset Quality Indicators) (Details) - USD ($) $ in Millions	Mar. 31, 2018		Dec. 31, 2017		Mar. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 221,614	[1]	$ 220,458	[1]	$ 212,826
Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	148,945		147,439		$ 140,662
Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	112,308		110,527
Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,835		28,978
Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,802		7,934
Pass [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	142,561		141,414
Pass [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	106,681		105,280
Pass [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,274		28,380
Pass [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,606		7,754
Special Mention [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	2,329		2,083
Special Mention [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	2,075		1,858
Special Mention [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	163		148
Special Mention [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	91		77
Substandard [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,948		3,868
Substandard [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,449		3,331
Substandard [Member] | Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	397		435
Substandard [Member] | Total commercial lending [Member] | Equipment Lease Financing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	102		102
Doubtful [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	107		74
Doubtful [Member] | Total commercial lending [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	103		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 $.9 billion, Loans of $.8 billion and Other assets of $.3 billion at March 31, 2018 and Loans held for sale of $1.7 billion, Loans of $.9 billion and Other assets of $.3 billion at December 31, 2017.