Significant Credit Concentrations (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Maximum Credit Exposure by Category
On-balance sheet	$ 32	$ 33
Individuals [Member]
Maximum Credit Exposure by Category
On-balance sheet	7	7
Financial Institutions [Member]
Maximum Credit Exposure by Category
On-balance sheet	2	1
Loans to affiliates and other
Maximum Credit Exposure by Category
On-balance sheet	11	14
Due from Affiliates [Member]
Maximum Credit Exposure by Category
On-balance sheet	1	1
Other Concentration [Member]
Maximum Credit Exposure by Category
On-balance sheet	$ 11	$ 10