Derivatives and Hedging Activities Non-designated Hedges Text description (Details) - Not Designated as Hedging Instrument [Member] $ in Millions	Dec. 31, 2017 USD ($) contracts	Dec. 31, 2016 USD ($) contracts
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held | contracts	142	136
Derivative, Notional Amount	$ 1,100.0	$ 1,100.0
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held | contracts	3	1
Derivative, Notional Amount	$ 0.2	$ 0.1
Loan Participations and Assignments [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held | contracts	6	2
Other Liabilities [Member] | Loan Participations and Assignments [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 48.0	$ 13.3
Other Assets [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 6.1	$ 6.1