Fair Value (Fair Value Measurements- Recurring Quantitative Information) (Details) - Fair Value, Measurements, Recurring $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 147,484	$ 103,035
Financial and nonfinancial liabilities, fair value disclosure	(4,518)	(3,506)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	5,882	5,137
Financial and nonfinancial liabilities, fair value disclosure	(463)	(318)
Recuring Assets, Net of Liabilities - Fair Value	5,419	4,819
Assets, fair value disclosure	5,900	5,100
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	109	132
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	$ 622	$ 434
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	3.60%	3.60%
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	74.20%	82.10%
Level 3 | Loans - Residential real estate | Consensus Pricing with Unobservable Inputs of credit and liquidity discount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		$ 60
Level 3 | Loans - Residential real estate | Consensus Pricing with Unobservable Inputs of credit and liquidity discount | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and liquidity discount		17.50%
Level 3 | Loans - Residential real estate | Consensus Pricing with Unobservable Inputs of credit and liquidity discount | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and liquidity discount		97.00%
Level 3 | Loans - Residential real estate | Consensus Pricing with Unobservable Inputs of credit and liquidity discount | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and liquidity discount		57.70%
Level 3 | Loans - Home equity | Consensus Pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 28	$ 21
Level 3 | Loans - Home equity | Consensus Pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative default rate	3.60%	3.60%
Level 3 | Loans - Home equity | 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 - Home equity | Consensus Pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cumulative default rate	75.80%	88.50%
Level 3 | Loans - Home equity | Consensus Pricing with Unobservable Inputs of credit and liquidity discount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 125
Level 3 | Loans - Home equity | Consensus Pricing with Unobservable Inputs of credit and liquidity discount | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and liquidity discount	0.50%
Level 3 | Loans - Home equity | Consensus Pricing with Unobservable Inputs of credit and liquidity discount | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and liquidity discount	100.00%
Level 3 | Loans - Home equity | Consensus Pricing with Unobservable Inputs of credit and liquidity discount | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit and liquidity discount	47.30%
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	$ 1,680	$ 1,263
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	5.0	0.050
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	14.4	0.159
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	8.8	0.087
Level 3 | Insignificant Assets, Net of Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 5
Financial and nonfinancial liabilities, fair value disclosure		$ 298
Residential Mortgages | 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	$ 1,078	$ 673
Residential Mortgages | 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	2.49%	3.25%
Residential Mortgages | 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	22.18%	27.83%
Residential Mortgages | 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	8.57%	9.22%
Commercial Mortgages | 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	$ 49	$ 57
Commercial Mortgages | 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	5.55%	6.30%
Commercial Mortgages | 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	159.90%	52.75%
Commercial Mortgages | 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	99.96%	34.06%
Commercial Mortgages | 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	$ 740	$ 569
Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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	$ 1,097	$ 1,365
Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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	1.63%	2.42%
Asset-backed | Level 3 | Securities available for sale | 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	$ 163	$ 199
Asset-backed | Level 3 | Securities available for sale | 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	1.82%	2.91%
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 and nonfinancial liabilities, fair value disclosure	$ (277)	$ (252)
Estimated growth rate of Visa Class A share price	16.00%	16.00%
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	161.80%	162.30%
Measurement Input, Constant Default Rate | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.000	0.000
Measurement Input, Constant Default Rate | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.169	0.122
Measurement Input, Constant Default Rate | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.046	0.047
Measurement Input, Constant Default Rate | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	0.014	0.010
Measurement Input, Constant Default Rate | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	0.200	0.060
Measurement Input, Constant Default Rate | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	0.032	0.033
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	0.060	0.080
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	0.000	0.000
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	1.000	1.000
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	0.069	0.112
Measurement Input, Loss Severity | Level 3 | Loans - Home equity | Consensus Pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.000	0.0
Measurement Input, Loss Severity | Level 3 | Loans - Home equity | Consensus Pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.984	0.984
Measurement Input, Loss Severity | Level 3 | Loans - Home equity | Consensus Pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.177	0.333
Measurement Input, Loss Severity | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.200	0.250
Measurement Input, Loss Severity | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.964	0.957
Measurement Input, Loss Severity | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.476	0.488
Measurement Input, Loss Severity | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	0.080	0.300
Measurement Input, Loss Severity | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	1.000	1.000
Measurement Input, Loss Severity | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	0.574	0.581
Measurement Input, Constant Prepayment Rate | Residential Mortgages | 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	0.000	0.000
Measurement Input, Constant Prepayment Rate | Residential Mortgages | 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	0.410	0.775
Measurement Input, Constant Prepayment Rate | Residential Mortgages | 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	0.126	0.211
Measurement Input, Constant Prepayment Rate | Commercial Mortgages | 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	0.050	0.040
Measurement Input, Constant Prepayment Rate | Commercial Mortgages | 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	0.155	0.161
Measurement Input, Constant Prepayment Rate | Commercial Mortgages | 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	0.055	0.049
Measurement Input, Constant Prepayment Rate | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.010	0.010
Measurement Input, Constant Prepayment Rate | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.307	0.376
Measurement Input, Constant Prepayment Rate | Residential mortgage-backed Securities | Level 3 | Securities available for sale | 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, measurement input	0.113	0.086
Measurement Input, Constant Prepayment Rate | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	0.010	0.010
Measurement Input, Constant Prepayment Rate | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	0.400	0.220
Measurement Input, Constant Prepayment Rate | Asset-backed | Level 3 | Securities available for sale | 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, measurement input	0.111	0.074
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	0.035	0.032
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	0.048	0.048
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	0.068	0.068
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	0.052	0.051
Measurement Input, Discount Rate | Level 3 | Loans - Home equity | Consensus Pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.048	0.048
Measurement Input, Discount Rate | Level 3 | Loans - Home equity | Consensus Pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.068	0.068
Measurement Input, Discount Rate | Level 3 | Loans - Home equity | Consensus Pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.060	0.063
Measurement Input, Discount Rate | Commercial Mortgages | 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	0.054	0.047
Measurement Input, Discount Rate | Commercial Mortgages | 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	0.080	0.078
Measurement Input, Discount Rate | Commercial Mortgages | 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	0.078	0.073