Fair Value (Fair Value Measurements- Recurring Quantitative Information) (Details) - Fair Value, Measurements, Recurring $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial derivatives - Swaps related to sales of certain Visa Class B common shares	$ (3,355)	$ (4,233)
Assets, Fair Value Disclosure	75,744	69,673
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Recurring, Fair Value Disclosure	6,100	6,400
Financial derivatives - Swaps related to sales of certain Visa Class B common shares	(333)	(531)
Assets, Fair Value Disclosure	6,157	6,475
Recuring Assets, Net of Liabilities - Fair Value	5,824	5,944
Level 3 | Loans - Residential real estate | Discounted Cash Flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	90	104
Level 3 | Loans - Residential real estate | Consensus Pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 129	$ 133
Level 3 | Loans - Residential real estate | Consensus Pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative default rate	11.00%	11.00%
Level 3 | Loans - Residential real estate | Consensus Pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative default rate	100.00%	100.00%
Level 3 | Loans - Residential real estate | Consensus Pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative default rate	81.80%	85.70%
Level 3 | Loans - Home equity | Consensus Pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 53	$ 61
Level 3 | Loans - Home equity | Consensus Pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and Liquidity discount	0.00%	0.00%
Level 3 | Loans - Home equity | Consensus Pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and Liquidity discount	99.00%	99.00%
Level 3 | Loans - Home equity | Consensus Pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and Liquidity discount	61.30%	61.10%
Level 3 | Equity Investments | Multiple of Adjusted Earnings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 1,255	$ 1,036
Level 3 | Equity Investments | Multiple of Adjusted Earnings | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multiple of earnings	4.5	4.5
Level 3 | Equity Investments | Multiple of Adjusted Earnings | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multiple of earnings	16.0	29.7
Level 3 | Equity Investments | Multiple of Adjusted Earnings | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multiple of earnings	8.4	8.3
Level 3 | Insignificant Assets, Net of Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 35	$ 58
Residential Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 1,257	$ 1,164
Residential Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	4.92%	3.90%
Residential Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	14.55%	18.39%
Residential Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	8.06%	8.30%
Commercial Mortgage | Level 3 | Loans Held For Sale | Discounted Cash Flow, Spread Over the Benchmark Curve
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 87	$ 107
Commercial Mortgage | Level 3 | Loans Held For Sale | Discounted Cash Flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	5.35%	5.25%
Commercial Mortgage | Level 3 | Loans Held For Sale | Discounted Cash Flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	19.00%	14.70%
Commercial Mortgage | Level 3 | Loans Held For Sale | Discounted Cash Flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	12.17%	10.20%
Commercial Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 726	$ 668
Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 2,128	$ 2,661
Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	2.16%	1.90%
Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 274	$ 332
Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spread over the benchmark curve	1.98%	1.79%
Visa Class B Swap | Level 3 | Financial Derivatives | Discounted Cash Flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial derivatives - Swaps related to sales of certain Visa Class B common shares	$ (210)	$ (380)
Estimated growth rate of Visa Class A share price	16.00%	16.00%
Estimated length of litigation resolution date	12/31/2020	6/30/2021
Visa Class B Swap | Level 3 | Financial Derivatives | Discounted Cash Flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated conversion factor of Class B shares into Class A shares	163.00%	163.80%
Measurement Input, Constant Default Rate | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.0000	0.0010
Measurement Input, Constant Default Rate | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.1880	0.1880
Measurement Input, Constant Default Rate | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.0510	0.0540
Measurement Input, Constant Default Rate | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.0100	0.0200
Measurement Input, Constant Default Rate | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.1850	0.1180
Measurement Input, Constant Default Rate | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.0400	0.0540
Measurement Input, Loss Severity | Level 3 | Loans - Residential real estate | Discounted Cash Flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, Measurement Input	0.0800	0.0800
Measurement Input, Loss Severity | Level 3 | Loans - Residential real estate | Consensus Pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, Measurement Input	0.0000	0.0000
Measurement Input, Loss Severity | Level 3 | Loans - Residential real estate | Consensus Pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, Measurement Input	1.0000	1.0000
Measurement Input, Loss Severity | Level 3 | Loans - Residential real estate | Consensus Pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, Measurement Input	0.1720	0.2060
Measurement Input, Loss Severity | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.1000	0.1500
Measurement Input, Loss Severity | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	1.0000	1.0000
Measurement Input, Loss Severity | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.5080	0.5150
Measurement Input, Loss Severity | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.1500	0.1500
Measurement Input, Loss Severity | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	1.0000	1.0000
Measurement Input, Loss Severity | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.6380	0.6850
Measurement Input, Constant Prepayment Rate | Residential Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.0000	0.0000
Measurement Input, Constant Prepayment Rate | Residential Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.5450	0.3670
Measurement Input, Constant Prepayment Rate | Residential Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.0870	0.1000
Measurement Input, Constant Prepayment Rate | Commercial Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.0460	0.0770
Measurement Input, Constant Prepayment Rate | Commercial Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.1470	0.1420
Measurement Input, Constant Prepayment Rate | Commercial Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.0570	0.0850
Measurement Input, Constant Prepayment Rate | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.0100	0.0100
Measurement Input, Constant Prepayment Rate | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.3300	0.3160
Measurement Input, Constant Prepayment Rate | Residential mortgage-backed Securities | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.1180	0.1080
Measurement Input, Constant Prepayment Rate | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.0100	0.0100
Measurement Input, Constant Prepayment Rate | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.1900	0.1900
Measurement Input, Constant Prepayment Rate | Asset backed | Level 3 | Available-for-sale Securities | Priced By A Third Party Vendor Using Discounted Cash Flow Pricing Model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Measurement Input	0.0850	0.0790
Measurement Input, Discount Rate | Level 3 | Loans - Residential real estate | Discounted Cash Flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, Measurement Input	0.0580	0.0490
Measurement Input, Discount Rate | Level 3 | Loans - Residential real estate | Consensus Pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, Measurement Input	0.0550	0.0550
Measurement Input, Discount Rate | Level 3 | Loans - Residential real estate | Consensus Pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, Measurement Input	0.0830	0.0800
Measurement Input, Discount Rate | Level 3 | Loans - Residential real estate | Consensus Pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, Measurement Input	0.0580	0.0570
Measurement Input, Discount Rate | Commercial Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.0690	0.0640
Measurement Input, Discount Rate | Commercial Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.0850	0.0790
Measurement Input, Discount Rate | Commercial Mortgage | Level 3 | Mortgage Servicing Rights | Discounted Cash Flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.0840	0.0780