Transactions with Affiliates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transactions [Abstract]
Loans to affiliates and other	$ 10,890	$ 10,345	$ 14,136
Average interest rate on loans to affiliates and other	1.52%	2.89%	2.79%
Due from affiliates	$ 6	$ 652	$ 210
Restricted cash with affiliates	120	116	93
Short-term debt to affiliates	$ 8,569	$ 6,225	$ 5,899
Average interest rate on short-term debt to affiliates	0.62%	2.33%	2.09%
Maximum month-end level of short-term borrowings during the year	$ 8,622	$ 7,087	$ 14,216
Long-term debt with affiliates	$ 822	$ 9,292	$ 7,523
Average interest rate long-term debt to affiliates	1.65%	3.17%	2.69%
Maximum month-end level of long-term borrowings during the year	$ 3,276	$ 13,391	$ 8,725
Due to affiliates	4,344	2,133	2,869
Maximum month-end level of loans to affiliates during the year	13,959	14,264	14,136
Interest income from affiliates and other	166	332	383
Interest expense to affiliates	75	433	225
Related Party Transaction [Line Items]
Other, net expense	(10)	(81)	(55)
Interest paid on short-term and long-term debt	112	421	198
Related Party [Member]
Related Party Transaction [Line Items]
Other, net expense	$ 2	$ 2	$ 2