Short-Term Debt (Narrative) (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Investment Securities And One To Four Family Residential Property Loans
Short-term Debt [Line Items]
Collateral pledged to the FHLB	$ 2.0	$ 1.9
City National
Short-term Debt [Line Items]
FHLB stock purchased during year	59,087
Unused and available FHLB funds	$ 1.6	$ 1.6