Derivative Instruments and Hedging Activities - Value of Derivative Assets and Derivative Liabilities (Details) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Other Assets
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	$ 4,814	$ 6,960
Other Assets | Interest rate swap contracts - commercial loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	4,814	6,960
Notional amount, Derivatives (included in Other Assets)	209,572	232,396
Collateral posted, Derivatives	0	0
Other Assets | Interest rate lock commitments - mortgage loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	452	236
Notional amount, Derivatives (included in Other Assets)	13,939	8,490
Other Assets | Forward sale contracts - mortgage loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	0	0
Notional amount, Derivatives (included in Other Assets)	0	0
Other Liabilities
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	4,786	6,958
Other Liabilities | Interest rate swap contracts - commercial loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	4,786	6,958
Notional amount, Derivatives (included in Other Liabilities)	209,572	232,396
Collateral posted, Derivatives	3,046	14,340
Other Liabilities | Interest rate lock commitments - mortgage loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	0	0
Notional amount, Derivatives (included in Other Liabilities)	0	0
Other Liabilities | Forward sale contracts - mortgage loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	16	27
Notional amount, Derivatives (included in Other Liabilities)	$ 14,564	$ 8,216