Deposit Liabilities Deposit Liabilities (Time Deposit Maturities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Maturities for Total Time Deposits [Line Items]
Time Deposits	$ 43,869	$ 31,795
One year, or less [Member]
Schedule of Maturities for Total Time Deposits [Line Items]
Time Deposits	28,764
Two years, or less [Member]
Schedule of Maturities for Total Time Deposits [Line Items]
Time Deposits	8,613
Three years, or less [Member]
Schedule of Maturities for Total Time Deposits [Line Items]
Time Deposits	3,579
Four years, or less [Member]
Schedule of Maturities for Total Time Deposits [Line Items]
Time Deposits	1,418
Five years, or less [Member]
Schedule of Maturities for Total Time Deposits [Line Items]
Time Deposits	1,495
Total deposits [Member]
Schedule of Maturities for Total Time Deposits [Line Items]
Time Deposits	$ 43,869