Asset Quality (Commercial Lending Asset Quality Indicators) (Details) - USD ($) $ in Millions	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 220,458	[1]	$ 210,833	[1]	$ 206,696
Total commercial lending
Financing Receivable, Recorded Investment [Line Items]
Total Loans	147,439		137,955		$ 133,544
Total commercial lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	110,527		101,364
Total commercial lending | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,978		29,010
Total commercial lending | Equipment Lease Financing
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,934		7,581
Pass | Total commercial lending
Financing Receivable, Recorded Investment [Line Items]
Total Loans	141,414		132,187
Pass | Total commercial lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	105,280		96,231
Pass | Total commercial lending | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28,380		28,561
Pass | Total commercial lending | Equipment Lease Financing
Financing Receivable, Recorded Investment [Line Items]
Total Loans	7,754		7,395
Special Mention | Total commercial lending
Financing Receivable, Recorded Investment [Line Items]
Total Loans	2,083		1,799
Special Mention | Total commercial lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	1,858		1,612
Special Mention | Total commercial lending | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	148		98
Special Mention | Total commercial lending | Equipment Lease Financing
Financing Receivable, Recorded Investment [Line Items]
Total Loans	77		89
Substandard | Total commercial lending
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,868		3,867
Substandard | Total commercial lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	3,331		3,449
Substandard | Total commercial lending | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	435		327
Substandard | Total commercial lending | Equipment Lease Financing
Financing Receivable, Recorded Investment [Line Items]
Total Loans	102		91
Doubtful | Total commercial lending
Financing Receivable, Recorded Investment [Line Items]
Total Loans	74		102
Doubtful | Total commercial lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	58		72
Doubtful | Total commercial lending | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	15		24
Doubtful | Total commercial lending | Equipment Lease Financing
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 1		$ 6

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.7 billion, Loans of $.9 billion, and Other assets of $.3 billion at December 31, 2017 and Loans held for sale of $2.4 billion, Loans of $.9 billion, and Other assets of $.5 billion at December 31, 2016.