Transactions with Affiliates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Parties Details [Abstract]
Loans to affiliates and other	$ 14,136	$ 14,527	$ 10,659
Average interest rate on loans to affiliates and other	2.79%	2.19%	1.78%
Due from affiliates	$ 210	$ 189	$ 997
Restricted cash with affiliates	93	100	0
Short-term debt to affiliates	$ 5,899	$ 5,997	$ 4,559
Average interest rate on short-term debt to affiliates	2.09%	1.04%	0.49%
Maximum month-end level of short-term borrowings during the year	$ 14,216	$ 8,377	$ 5,091
Long-term debt with affiliates	$ 7,523	$ 270	$ 0
Average interest rate long-term debt to affiliates	2.69%	0.23%	0.00%
Maximum month-end level of long-term borrowings during the year	$ 8,725	$ 270	$ 0
Due to affiliates	2,869	1,988	1,517
Maximum month-end level of loans to affiliates during the year	14,136	14,527	13,083
Interest income from affiliates and other	383	279	207
Interest expense to affiliates	225	58	24
Related Party Transaction [Line Items]
Other, net	(55)	15	14
Interest paid on short term and long-term debt to affiliates	198	54	21
Related Party [Member]
Related Party Transaction [Line Items]
Other, net	$ 2	$ 2	$ 1