Fair Value Measurements - Changes in Unrealized Gains (Losses) Included in Net Income for Financial Instruments Classified as Level 3 Still Held at Year End (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses)	Net realized gains (losses)
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	$ 3	$ (8)
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | Other Comprehensive Income (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	(5)	26
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | Securities available-for-sale and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	0
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | Securities available-for-sale and other | Other Comprehensive Income (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	(5)	26
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | Collateralized Loan Obligations [Member] | Fair Value Option, Other Eligible Items
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	3	(8)
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | Collateralized Loan Obligations [Member] | Fair Value Option, Other Eligible Items | Other Comprehensive Income (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	0
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | CMBS | Securities available-for-sale and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	0
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | CMBS | Securities available-for-sale and other | Other Comprehensive Income (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	10	(5)
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | Corporate | Securities available-for-sale and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	0
Fair Value, Recurring [Member] | Significant Unobservable Inputs (Level 3) | Corporate | Securities available-for-sale and other | Other Comprehensive Income (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	$ (15)	$ 31