Securities (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($) security	Dec. 31, 2015 USD ($) 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	$ 559.0	$ 346.1
Amortized cost of callable debt securities	122.5
Fair value of callable debt securities	$ 118.5
Number of securities in a continuous unrealized loss position total | security	20	26
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	10	10
Securities in unrealized loss position, number of companies issuing securities | security	7
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	$ (1.5)
Minimum [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Callable Debt Securities, Maturity Period	5 months
Callable Debt Securities, Call Feature, Period	1 month
Maximum [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Callable Debt Securities, Maturity Period	20 years
Callable Debt Securities, Call Feature, Period	5 years