Transactions with Affiliates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transactions [Abstract]
Loans to affiliates and other	$ 10,345	$ 14,136	$ 14,527
Average interest rate on loans to affiliates and other	2.89%	2.79%	2.19%
Due from affiliates	$ 652	$ 210	$ 189
Restricted cash with affiliates	116	93	100
Short-term debt to affiliates	$ 6,225	$ 5,899	$ 5,997
Average interest rate on short-term debt to affiliates	2.33%	2.09%	1.04%
Maximum month-end level of short-term borrowings during the year	$ 7,087	$ 14,216	$ 8,377
Long-term debt with affiliates	$ 9,292	$ 7,523	$ 270
Average interest rate long-term debt to affiliates	3.17%	2.69%	0.23%
Maximum month-end level of long-term borrowings during the year	$ 13,391	$ 8,725	$ 270
Due to affiliates	2,133	2,869	1,988
Maximum month-end level of loans to affiliates during the year	14,264	14,136	14,527
Interest income from affiliates and other	332	383	279
Interest expense to affiliates	433	225	58
Related Party Transaction [Line Items]
Other, net expense	(81)	(55)	15
Interest paid on short-term and long-term debt	421	198	54
Related Party [Member]
Related Party Transaction [Line Items]
Other, net expense	$ 2	$ 2	$ 2