Investment Securities Pledged Securities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investments [Abstract]
Carrying value of available-for-sale securities pledged to secure public and trust department deposits and repurchase agreements	$ 303.8	$ 260.9
Carrying value of held-to-maturity securities pledged to secure public and trust department deposits and repurchase agreements	21.4	45.3
Carrying value of available-for-sale securities pledged to secure additional borrowing capacity at FHLB and FRB	16.2	50.4
Carrying value of held-to-maturity securities pledged to secure additional borrowing capacity at FHLB and FRB	$ 25.9