Investments (Collectively Significant Equity Method Investments - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Carrying value of investments accounted for under the equity method	$ 2,800
Total assets	247,869	$ 227,259
Total liabilities	229,781	211,022
Net income (loss)	(1,061)	(740)	$ 865
Nonconsolidated Equity Method Investment
Schedule of Equity Method Investments [Line Items]
Unfunded commitments	1,500
Total assets	504,000	404,000
Total liabilities	63,000	52,800
Net income (loss)	$ 37,700	$ 33,300	$ 33,300