Related Party Transactions (Service Agreements - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Other expenses	$ 1,360	$ 1,297	$ 3,738	$ 3,680
Revenues	8,450	10,810	27,487	28,193
Net receivables (payables) due from (to) affiliates	(136)		(136)		$ (250)
Affiliated Entity | Services Necessary To Conduct The Company's Activities
Related Party Transaction [Line Items]
Other expenses	577	694	1,800	2,100
Revenues	$ 11	$ 7	$ 30	$ 21