Deposits (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deposits [Abstract]
Time Deposits, $100,000 or More	$ 3,900	$ 3,500
Time deposit accounts with balances of $250,000 or more	2,100	$ 1,600
Public funds deposits included in deposits	2,100
Interest-bearing Domestic Deposit, Brokered	1,900
Carrying value of investment securities available for sale pledged as security for public funds deposits	1,200
Letter of Credit issued by FHLB pledged as security for public funds deposits	$ 4