Significant Credit Concentrations (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Maximum Credit Exposure by Category
On-balance sheet	$ 37	$ 40
Loans to Affiliates and Other [Member]
Maximum Credit Exposure by Category
On-balance sheet	10	14
Institutions [Member]
Maximum Credit Exposure by Category
On-balance sheet	13	14
Individuals [Member]
Maximum Credit Exposure by Category
On-balance sheet	12	11
Financial Services [Member]
Maximum Credit Exposure by Category
On-balance sheet	1	1
Due from Affiliates [Member]
Maximum Credit Exposure by Category
On-balance sheet	$ 1	$ 0