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	235,288	$ 216,153
Total liabilities	217,173	197,674
Net income (loss)	(1,306)	(809)	$ 967
Nonconsolidated Equity Method Investment
Schedule of Equity Method Investments [Line Items]
Unfunded commitments	1,500
Total assets	503,700	403,600
Total liabilities	62,900	52,700
Net income (loss)	$ 37,700	$ 33,300	$ 33,300