Securities (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Fair Value of Available for Sale and Held to Maturity securities pledged as collateral	$ 729.6	$ 736.2
Amortized cost of callable debt securities	150.3
Fair value of callable debt securities	$ 144.2
Number of securities in a continuous unrealized loss position total | security	57	57
Individual name issuer trust preferred debt securities
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Number of securities in a continuous unrealized loss position total | security	9	10
Securities in unrealized loss position, number of companies issuing securities | security	6
Amortized cost of trust preferred securities of individual name issuers that are below investment grade	$ 10.9
Unrealized losses of trust preferred securities of individual name issuers that are below investment grade	$ (1.2)
Minimum [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Maturity period of callable debt securities	14 months
Call features of callable debt securities	1 month
Maximum [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Maturity period of callable debt securities	20 years
Call features of callable debt securities	4 years