Investments (Collectively Significant Equity Method Investments - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 25,200								$ 25,200
Unfunded Commitments For Investments Accounted For Under Equity Method	6,700								6,700
Total Assets	687,584				$ 663,072				687,584	$ 663,072
Total Liabilities	657,331				632,947				657,331	632,947
Net income (loss)	614	$ 495	$ 408	$ 85	1,581	$ 1,167	$ 915	$ 1,639	1,602	5,302	$ 6,876
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets	1,200,000				1,200,000				1,200,000	1,200,000
Total Liabilities	$ 148,000				$ 148,900				148,000	148,900
Net income (loss)									$ 32,800	$ (11,800)	$ 231,000