Fair Value (Fair Value Measurements- Recurring Quantitative Information) (Details) - Fair Value, Measurements, Recurring [Member] - Level 3 [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 7,400	$ 8,800
Recurring Liabilities - Fair Value	(300)	(400)
Total Recurring Assets Net of Recurring Liabilities - Fair Value	7,069	8,397
Loans Held For Sale [Member] | Commercial Mortgage [Member] | Discounted Cash Flow [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 758	$ 1,400
Loans Held For Sale [Member] | Commercial Mortgage [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	0.00%	0.42%
Estimated servicing cash flows	0.30%	0.00%
Loans Held For Sale [Member] | Commercial Mortgage [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	40.45%	17.25%
Estimated servicing cash flows	5.10%	7.30%
Loans Held For Sale [Member] | Commercial Mortgage [Member] | Discounted Cash Flow [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	12.57%	3.62%
Estimated servicing cash flows	1.10%	1.50%
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 2,845	$ 3,254
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	1.00%	1.00%
Constant default rate (CDR)	0.10%	0.00%
Loss Severity	20.00%	10.00%
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	24.70%	24.20%
Constant default rate (CDR)	14.60%	16.70%
Loss Severity	96.70%	98.50%
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	8.70%	7.20%
Constant default rate (CDR)	5.20%	5.30%
Loss Severity	52.50%	53.50%
Spread over the benchmark curve	1.60%	2.36%
Available-for-sale Securities [Member] | Asset backed [Member] | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 348	$ 403
Available-for-sale Securities [Member] | Asset backed [Member] | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	1.00%	1.00%
Constant default rate (CDR)	2.00%	2.00%
Loss Severity	24.20%	24.20%
Available-for-sale Securities [Member] | Asset backed [Member] | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	18.00%	16.00%
Constant default rate (CDR)	13.90%	13.90%
Loss Severity	100.00%	100.00%
Available-for-sale Securities [Member] | Asset backed [Member] | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	6.90%	6.40%
Constant default rate (CDR)	6.20%	6.60%
Loss Severity	73.60%	77.30%
Spread over the benchmark curve	1.62%	2.78%
Loans - Residential real estate [Member] | Discounted Cash Flow [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 101	$ 116
Loans - Residential real estate [Member] | Discounted Cash Flow [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss Severity	8.00%	8.00%
Discount rate	4.60%	4.20%
Loans - Residential real estate [Member] | Consensus Pricing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 125	$ 141
Loans - Residential real estate [Member] | Consensus Pricing [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative default rate	11.00%	11.00%
Loss Severity	0.00%	0.00%
Discount rate	5.50%	4.70%
Loans - Residential real estate [Member] | Consensus Pricing [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative default rate	100.00%	100.00%
Loss Severity	100.00%	100.00%
Discount rate	8.00%	6.70%
Loans - Residential real estate [Member] | Consensus Pricing [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative default rate	85.60%	86.90%
Loss Severity	21.20%	22.90%
Discount rate	5.70%	5.10%
Loans - Home equity [Member] | Consensus Pricing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 65	$ 78
Loans - Home equity [Member] | Consensus Pricing [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and Liquidity discount	0.00%	0.00%
Loans - Home equity [Member] | Consensus Pricing [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and Liquidity discount	99.00%	99.00%
Loans - Home equity [Member] | Consensus Pricing [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and Liquidity discount	60.40%	57.90%
Equity Investments [Member] | Consensus Pricing [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidity Discount		0.00%
Equity Investments [Member] | Consensus Pricing [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidity Discount		40.00%
Equity Investments [Member] | Multiple Of Adjusted Earnings [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 1,061
Equity Investments [Member] | Multiple Of Adjusted Earnings [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multiple of earnings	4.5	4.5
Equity Investments [Member] | Multiple Of Adjusted Earnings [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multiple of earnings	29.7	12.0
Equity Investments [Member] | Multiple Of Adjusted Earnings [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multiple of earnings	8.4	7.8
Equity Investments [Member] | Multiple Of Adjusted Earnings and Consensus Pricing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value		$ 1,331
Mortgage Servicing Rights [Member] | Residential Mortgage [Member] | Discounted Cash Flow [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 1,226	$ 1,182
Mortgage Servicing Rights [Member] | Residential Mortgage [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	0.00%	0.00%
Spread over the benchmark curve	3.29%	3.41%
Mortgage Servicing Rights [Member] | Residential Mortgage [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	39.70%	36.00%
Spread over the benchmark curve	17.84%	19.13%
Mortgage Servicing Rights [Member] | Residential Mortgage [Member] | Discounted Cash Flow [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	10.20%	9.40%
Spread over the benchmark curve	8.27%	8.50%
Mortgage Servicing Rights [Member] | Commercial Mortgage [Member] | Discounted Cash Flow [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 628	$ 576
Mortgage Servicing Rights [Member] | Commercial Mortgage [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	7.70%	7.50%
Discount rate	6.20%	3.50%
Mortgage Servicing Rights [Member] | Commercial Mortgage [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	13.60%	43.40%
Discount rate	7.70%	7.60%
Mortgage Servicing Rights [Member] | Commercial Mortgage [Member] | Discounted Cash Flow [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Constant prepayment rate (CPR)	8.50%	8.60%
Discount rate	7.60%	7.50%
Other Assets [Member] | BlackRock Series C Preferred Stock | Consensus Pricing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value		$ 232
Other Assets [Member] | BlackRock Series C Preferred Stock | Consensus Pricing [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidity Discount		15.00%
Other Assets [Member] | BlackRock Series C Preferred Stock | Consensus Pricing [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidity Discount		25.00%
Other Assets [Member] | BlackRock Series C Preferred Stock | Consensus Pricing [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidity Discount		20.00%
Financial Derivatives [Member] | BlackRock LTIP [Member] | Consensus Pricing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Liabilities - Fair Value		$ (232)
Financial Derivatives [Member] | BlackRock LTIP [Member] | Consensus Pricing [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidity Discount		15.00%
Financial Derivatives [Member] | BlackRock LTIP [Member] | Consensus Pricing [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidity Discount		25.00%
Financial Derivatives [Member] | BlackRock LTIP [Member] | Consensus Pricing [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidity Discount		20.00%
Financial Derivatives [Member] | Visa Class B Swap [Member] | Discounted Cash Flow [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Liabilities - Fair Value	$ (149)	$ (164)
Estimated growth rate of Visa Class A share price	14.00%	14.00%
Estimated length of litigation resolution date	Jun. 30, 2019	Jun. 30, 2019
Financial Derivatives [Member] | Visa Class B Swap [Member] | Discounted Cash Flow [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated conversion factor of Class B shares into Class A shares	164.50%	164.40%
Insignificant Assets, Net of Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 61	$ 80