Investment Securities (Pledged Securities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Securities
Pledged Financial Instruments, Not Separately Reported, Held-To-Maturity Securities for Federal Home Loan Bank and Federal Reserve Bank	$ 25.6	$ 25.9
Carrying value of available-for-sale securities pledged to secure public and trust department deposits and repurchase agreements	326.0	303.8
Carrying value of held-to-maturity securities pledged to secure public and trust department deposits and repurchase agreements	23.2	21.4
Carrying value of available-for-sale securities pledged to secure additional borrowing capacity at Federal Home Loan Bank and Federal Reserve Bank	$ 15.6	$ 16.2