Fair Value (Fair Value Measurements - Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		$ 1,045	$ 1,071
Debt securities, available-for-sale, fair value	[1]	33,122	29,830
Derivative contracts in a receivable position		7	16
Derivative contracts in a payable position		$ 57	$ 31
Investment in any one industry did not exceed percentage		9.00%	11.00%
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		$ 33,122	$ 29,830
Derivative contracts in a receivable position		9	17
Total assets		34,286	31,017
Derivative contracts in a payable position		61	33
Total liabilities		61	33
Fair value, measurements, recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		2
Fair value, measurements, recurring | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position			1
Fair value, measurements, recurring | Credit contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		55	28
Fair value, measurements, recurring | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		4	4
Fair value, measurements, recurring | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		1,045	1,071
Fair value, measurements, recurring | U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		1,743	803
Fair value, measurements, recurring | U.S. States and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		858	1,095
Fair value, measurements, recurring | Foreign government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		161	176
Fair value, measurements, recurring | Agency mortgage-backed securities | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		19,706	18,588
Fair value, measurements, recurring | Agency mortgage-backed securities | Commercial Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		4,736	4,189
Fair value, measurements, recurring | Mortgage-backed residential
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		3,479	2,640
Fair value, measurements, recurring | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		547	425
Fair value, measurements, recurring | Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		1,892	1,914
Fair value, measurements, recurring | Mortgage loans held-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held-for-sale, fair value		102	91
Fair value, measurements, recurring | Consumer other | Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net		8	8
Fair value, measurements, recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		7	16
Fair value, measurements, recurring | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		1	1
Fair value, measurements, recurring | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		1
Fair value, measurements, recurring | Fair value, inputs, level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		1,758	820
Derivative contracts in a receivable position		1	0
Total assets		2,793	1,884
Derivative contracts in a payable position		4	4
Total liabilities		4	4
Fair value, measurements, recurring | Fair value, inputs, level 1 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position			0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Credit contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		4	4
Fair value, measurements, recurring | Fair value, inputs, level 1 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		1,034	1,064
Fair value, measurements, recurring | Fair value, inputs, level 1 | U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		1,743	803
Fair value, measurements, recurring | Fair value, inputs, level 1 | U.S. States and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Foreign government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		15	17
Fair value, measurements, recurring | Fair value, inputs, level 1 | Agency mortgage-backed securities | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Agency mortgage-backed securities | Commercial Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Mortgage-backed residential
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Mortgage loans held-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Consumer other | Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		0	0
Fair value, measurements, recurring | Fair value, inputs, level 1 | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		1
Fair value, measurements, recurring | Fair value, inputs, level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		31,357	29,003
Derivative contracts in a receivable position		3	1
Total assets		31,462	29,004
Derivative contracts in a payable position		0	1
Total liabilities		0	1
Fair value, measurements, recurring | Fair value, inputs, level 2 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		0
Fair value, measurements, recurring | Fair value, inputs, level 2 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position			1
Fair value, measurements, recurring | Fair value, inputs, level 2 | Credit contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		0	0
Fair value, measurements, recurring | Fair value, inputs, level 2 | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		0	0
Fair value, measurements, recurring | Fair value, inputs, level 2 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		0	0
Fair value, measurements, recurring | Fair value, inputs, level 2 | U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 2 | U.S. States and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		851	1,088
Fair value, measurements, recurring | Fair value, inputs, level 2 | Foreign government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		146	159
Fair value, measurements, recurring | Fair value, inputs, level 2 | Agency mortgage-backed securities | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		19,706	18,588
Fair value, measurements, recurring | Fair value, inputs, level 2 | Agency mortgage-backed securities | Commercial Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		4,736	4,189
Fair value, measurements, recurring | Fair value, inputs, level 2 | Mortgage-backed residential
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		3,479	2,640
Fair value, measurements, recurring | Fair value, inputs, level 2 | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		547	425
Fair value, measurements, recurring | Fair value, inputs, level 2 | Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		1,892	1,914
Fair value, measurements, recurring | Fair value, inputs, level 2 | Mortgage loans held-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held-for-sale, fair value		102	0
Fair value, measurements, recurring | Fair value, inputs, level 2 | Consumer other | Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net		0	0
Fair value, measurements, recurring | Fair value, inputs, level 2 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		2	0
Fair value, measurements, recurring | Fair value, inputs, level 2 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		1	1
Fair value, measurements, recurring | Fair value, inputs, level 2 | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		0
Fair value, measurements, recurring | Fair value, inputs, level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		7	7
Derivative contracts in a receivable position		5	16
Total assets		31	129
Derivative contracts in a payable position		57	28
Total liabilities		57	28
Fair value, measurements, recurring | Fair value, inputs, level 3 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		2
Fair value, measurements, recurring | Fair value, inputs, level 3 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position			0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Credit contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		55	28
Fair value, measurements, recurring | Fair value, inputs, level 3 | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a payable position		0	0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities		11	7
Fair value, measurements, recurring | Fair value, inputs, level 3 | U.S. Treasury and federal agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 3 | U.S. States and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		7	7
Fair value, measurements, recurring | Fair value, inputs, level 3 | Foreign government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Agency mortgage-backed securities | Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Agency mortgage-backed securities | Commercial Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Mortgage-backed residential
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, fair value		0	0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Mortgage loans held-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held-for-sale, fair value		0	91
Fair value, measurements, recurring | Fair value, inputs, level 3 | Consumer other | Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net		8	8
Fair value, measurements, recurring | Fair value, inputs, level 3 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		5	16
Fair value, measurements, recurring | Fair value, inputs, level 3 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		0	$ 0
Fair value, measurements, recurring | Fair value, inputs, level 3 | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contracts in a receivable position		$ 0

[1] Refer to Note 6 for discussion of investment securities pledged as collateral.