Fair Value (Fair Value Measurements - Recurring Quantitative Information) (Details) $ in Millions	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	$ 40,590	$ 44,159
Fair value	4,006	3,423
Derivative Liability	(5,225)	(4,524)
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	40,590	44,159
Loans, fair value	1,244	1,310
Equity investments	2,618	3,147
Derivative Liability	(8,220)	(7,618)
Recurring assets - fair value	56,118	59,135
Residential mortgage-backed non-agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	713	819
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total recurring assets net of recurring liabilities - fair value	7,208	6,831
Level 3 | Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	967	1,001
Loans, fair value	738	769
Equity investments	1,729	1,778
Derivative Liability	(108)	(123)
Recurring assets - fair value	7,573	7,252
Level 3 | Commercial mortgage loans held for sale | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, fair value	25	33
Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	713	819
Level 3 | Asset-backed | Priced by a third-party vendor using a discounted cash flow pricing model
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	103	124
Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, fair value	555	570
Level 3 | Loans - Residential real estate | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, fair value	75	76
Level 3 | Loans - Home equity - First-lien | Consensus pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, fair value	19	25
Level 3 | Loans - Home equity | Consensus pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, fair value	89	98
Level 3 | Equity investments | Multiple of adjusted earnings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	1,729	1,778
Level 3 | Residential mortgage servicing rights | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	2,837	2,310
Level 3 | Commercial mortgage servicing rights | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	1,169	1,113
Level 3 | Financial derivatives | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	(99)	(107)
Level 3 | Insignificant Assets, Net of Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Insignificant assets, fair value disclosure	$ (7)	$ (8)
Spread over the benchmark curve | Level 3 | Commercial mortgage loans held for sale | Discounted cash flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.0585	0.0585
Spread over the benchmark curve | Level 3 | Commercial mortgage loans held for sale | Discounted cash flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.7140	0.2465
Spread over the benchmark curve | Level 3 | Commercial mortgage loans held for sale | Discounted cash flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.2611	0.0959
Spread over the benchmark curve | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.0250	0.0289
Spread over the benchmark curve | Level 3 | Asset-backed | Priced by a third-party vendor using a discounted cash flow pricing model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.0256	0.0296
Spread over the benchmark curve | Level 3 | Residential mortgage servicing rights | Discounted cash flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input	0.0337	0.0254
Spread over the benchmark curve | Level 3 | Residential mortgage servicing rights | Discounted cash flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input	0.1650	0.1653
Spread over the benchmark curve | Level 3 | Residential 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	0.0765	0.0766
Constant prepayment rate | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a 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
Constant prepayment rate | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.279	0.279
Constant prepayment rate | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.038	0.099
Constant prepayment rate | Level 3 | Asset-backed | Priced by a third-party vendor using a 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
Constant prepayment rate | Level 3 | Asset-backed | Priced by a third-party vendor using a discounted cash flow pricing model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.110	0.400
Constant prepayment rate | Level 3 | Asset-backed | Priced by a third-party vendor using a discounted cash flow pricing model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.053	0.075
Constant prepayment rate | Level 3 | Residential 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
Constant prepayment rate | Level 3 | Residential mortgage servicing rights | Discounted cash flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input	0.297	0.345
Constant prepayment rate | Level 3 | Residential 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	0.058	0.067
Constant prepayment rate | Level 3 | Commercial mortgage servicing rights | Discounted cash flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input	0.052	0.039
Constant prepayment rate | Level 3 | Commercial mortgage servicing rights | Discounted cash flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input	0.074	0.098
Constant prepayment rate | Level 3 | Commercial 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	0.054	0.043
Constant default rate | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a 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
Constant default rate | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.120	0.130
Constant default rate | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.028	0.040
Constant default rate | Level 3 | Asset-backed | Priced by a third-party vendor using a 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
Constant default rate | Level 3 | Asset-backed | Priced by a third-party vendor using a discounted cash flow pricing model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.043	0.073
Constant default rate | Level 3 | Asset-backed | Priced by a third-party vendor using a discounted cash flow pricing model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.017	0.021
Loss severity | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.100	0.150
Loss severity | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.714	0.800
Loss severity | Level 3 | Residential mortgage-backed non-agency securities | Priced by a third-party vendor using a discounted cash flow pricing model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.421	0.461
Loss severity | Level 3 | Asset-backed | Priced by a third-party vendor using a discounted cash flow pricing model | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.300	0.200
Loss severity | Level 3 | Asset-backed | Priced by a third-party vendor using a 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
Loss severity | Level 3 | Asset-backed | Priced by a third-party vendor using a discounted cash flow pricing model | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, measurement input	0.488	0.490
Loss severity | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.000	0.000
Loss severity | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	1.000	1.000
Loss severity | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.054	0.062
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]
Financing receivable, measurement input	0.060	0.060
Loss severity | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.000	0.000
Loss severity | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	1.000	1.000
Loss severity | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.152	0.153
Cumulative default rate | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.036	0.036
Cumulative default rate | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	1.000	1.000
Cumulative default rate | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.596	0.662
Cumulative default rate | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.036	0.036
Cumulative default rate | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	1.000	1.000
Cumulative default rate | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.633	0.725
Discount rate | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.055	0.055
Discount rate | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.075	0.075
Discount rate | Level 3 | Loans - Residential real estate - Uninsured | Consensus pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.058	0.059
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]
Financing receivable, measurement input	0.084	0.079
Discount rate | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.055	0.055
Discount rate | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.075	0.075
Discount rate | Level 3 | Loans - Home equity - First-lien | Consensus pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.063	0.065
Discount rate | Level 3 | Commercial mortgage servicing rights | Discounted cash flow | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input	0.083	0.078
Discount rate | Level 3 | Commercial mortgage servicing rights | Discounted cash flow | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input	0.107	0.101
Discount rate | Level 3 | Commercial 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	0.102	0.098
Credit and liquidity discount | Level 3 | Loans - Home equity | Consensus pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.004	0.004
Credit and liquidity discount | Level 3 | Loans - Home equity | Consensus pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	1.000	1.000
Credit and liquidity discount | Level 3 | Loans - Home equity | Consensus pricing | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing receivable, measurement input	0.447	0.462
Multiple of earnings | Level 3 | Equity investments | Multiple of adjusted earnings | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, measurement input	0.045	0.045
Multiple of earnings | Level 3 | Equity investments | Multiple of adjusted earnings | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, measurement input	0.200	0.250
Multiple of earnings | Level 3 | Equity investments | Multiple of adjusted earnings | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, measurement input	0.097	0.091
Estimated Conversion Factor | Level 3 | Financial derivatives | Discounted cash flow | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	1.59	1.61
Estimated Annual Growth Rate | Level 3 | Financial derivatives | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.160	0.160