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Capital Structure - Narrative (Details) - USD ($) |  |  |  |  |  | 9 Months Ended |
--- | --- | --- | --- | --- | --- | --- | ---
Jun. 15, 2023 | May 18, 2023 | Apr. 17, 2023 | Mar. 31, 2023 | Mar. 29, 2023 | Sep. 30, 2023 | Dec. 31, 2022
Debt outstanding: |  |  |  |  |  |  |
Preferred stock, par value (in dollars per share) |  |  |  |  |  | $ 1 | $ 1
Redemption of preferred stock |  |  | $ 575,000,000 |  |  |  |
Preferred stock, shares issued (in shares) |  |  |  |  |  | 82,000 | 81,000
Series G Noncumulative Preferred Stock |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Stock redeemed (in shares) |  |  | 23,000 |  |  |  |
Preferred stock, par value (in dollars per share) |  |  | $ 1.00 |  |  |  |
Liquidation preference amount (in dollars per shares) |  |  | $ 25,000 |  |  |  |
Preferred stock dividends |  |  | $ 18,000,000 |  |  |  |
Series J Noncumulative Preferred Stock |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Preferred stock, par value (in dollars per share) |  | $ 1.00 |  |  |  |  |
Liquidation preference amount (in dollars per shares) |  | $ 25,000 |  |  |  |  |
Preferred stock, shares issued (in shares) |  | 24,000 |  |  |  |  |
Gross proceeds |  | $ 600,000,000 |  |  |  |  |
Preferred stock, redemption price par value (in dollars per share) |  | $ 25,000 |  |  |  |  |
Period after occurrence of certain tax and rating agency events in which redemption of debt in whole permissible |  | 90 days |  |  |  |  |
Series J Noncumulative Preferred Stock | Preferred Stock, Redemption, Period Three |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Preferred stock, redemption price par value (in dollars per share) |  | $ 25,000 |  |  |  |  |
Series J Noncumulative Preferred Stock | Preferred Stock, Redemption, Period One |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Preferred stock, redemption price par value (in dollars per share) |  | $ 25,500 |  |  |  |  |
Series J Noncumulative Preferred Stock | Preferred Stock, Redemption, Period Two |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Number of days after regulatory capital event |  | 90 days |  |  |  |  |
Senior Notes |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Repayments of debt | $ 500,000,000 |  |  | $ 500,000,000 | $ 250,000,000 |  |
Senior Notes | Senior Notes Due 2033 at 5.25 Percent |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Issuance of debt |  |  |  | $ 750,000,000 |  |  |
Subsequent acquisition (in percentage) |  |  |  | 5.25% |  |  |
Senior Notes | London Interbank Offered Rate (LIBOR) |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Basis spread on interest at floating rate | 3.15% |  |  |  | 0.63% |  |
5.100% Fixed-to-Floating Rate Subordinated Debentures due 2053 |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Subsequent acquisition (in percentage) |  |  |  |  |  | 5.10% |
5.100% Fixed-to-Floating Rate Subordinated Debentures due 2053 | London Interbank Offered Rate (LIBOR) |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Basis spread on interest at floating rate |  |  |  |  |  | 3.165% |
5.750% Subordinated Debentures, due 2053 |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Subsequent acquisition (in percentage) |  |  |  |  |  | 5.75% |
5.750% Subordinated Debentures, due 2053 | London Interbank Offered Rate (LIBOR) |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Basis spread on interest at floating rate |  |  |  |  |  | 2.938% |
Subordinated Debt |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Maximum period for deferment of interest payment |  |  |  |  |  | 5 years |
Subordinated Debt | Secured Overnight Financing Rate (SOFR) |  |  |  |  |  |  |
Debt outstanding: |  |  |  |  |  |  |
Basis spread on interest at floating rate |  |  |  |  |  | 0.26161% |

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