Derivatives and Hedging Activities Non-designated Hedges Text description (Details) - Derivatives not designated as hedging instruments: $ in Millions	Dec. 31, 2018 USD ($) contracts	Dec. 31, 2017 USD ($) contracts
Derivatives - interest rate swaps
Derivative [Line Items]
Derivative number of instruments | contracts	160	142
Derivative notional amount | $	$ 1,300.0	$ 1,100.0
Foreign exchange contracts
Derivative [Line Items]
Derivative number of instruments | contracts	2	3
Derivative notional amount | $	$ 0.1	$ 0.2
Risk participation agreements - executed by other financial institutions
Derivative [Line Items]
Derivative number of instruments | contracts	7	6
Derivative notional amount | $	$ 59.8	$ 48.0
Risk participation agreements - executed by the Bank
Derivative [Line Items]
Derivative number of instruments | contracts	4	2
Derivative notional amount | $	$ 20.7	$ 6.1