Fair Value (Fair Value Measurements - Recurring Quantitative Information) (Details) $ in Millions	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	$ 42,280	$ 41,785
Fair value	3,762	3,686
Derivative Liability	(3,922)	(3,538)
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	42,280	41,785
Loans, fair value	1,217	1,238
Equity investments	2,739	2,717
Derivative Liability	(6,365)	(5,899)
Recurring assets - fair value	57,050	56,862
Residential mortgage-backed non-agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	668	696
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total recurring assets net of recurring liabilities - fair value	7,244	7,050
Level 3 | Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities – available for sale	924	956
Loans, fair value	713	726
Equity investments	2,030	1,952
Derivative Liability	(113)	(152)
Recurring assets - fair value	7,555	7,448
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	11	11
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	668	696
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	100	102
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	539	546
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	73	75
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	17	18
Level 3 | Loans - Home equity | Consensus pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, fair value	84	87
Level 3 | Equity investments | Multiple of adjusted earnings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	2,030	1,952
Level 3 | Residential mortgage servicing rights | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	2,687	2,654
Level 3 | Commercial mortgage servicing rights | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	1,075	1,032
Level 3 | Financial derivatives | Discounted cash flow
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	(106)	(145)
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	$ 66	$ 22
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	0.0580	0.0575
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	0.7155	0.3610
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	0.2649	0.1647
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	0.0268	0.0285
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	0.0227	0.0248
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	0.0337
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	0.1648	0.1668
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	0.0766	0.0765
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	0.029	0.037
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	0.280	0.280
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	0.041	0.051
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	0.401	0.336
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	0.063	0.064
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	0.050	0.053
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	0.086	0.097
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	0.052	0.055
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	0.120
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	0.019	0.027
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	0.081	0.043
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	0.016	0.017
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	0.100
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	0.700	0.690
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	0.423	0.412
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	0.497	0.495
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	0.053	0.054
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	0.138	0.144
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	0.582	0.591
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	0.607	0.609
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	0.058
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	0.080	0.078
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	0.061	0.062
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	0.080	0.076
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	0.103	0.100
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	0.099	0.096
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	0.003	0.003
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	0.437	0.438
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	0.055	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	0.270	0.267
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	0.104	0.101
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	1.59
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