Derivative Financial Instruments (Details 2) - Non-hedging derivative financial instruments - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Financial Instruments
Gain (loss)	$ 1,402	$ 999	$ 1,237
Interest rate swap contracts | Other expense
Derivative Financial Instruments
Gain (loss)	26	64	(8)
Interest rate swap contracts | Other income
Derivative Financial Instruments
Gain (loss)	1,585	730	1,045
Loan commitments | Mortgage banking income
Derivative Financial Instruments
Gain (loss)	23	(4)	45
Forward contracts - mortgage loan | Mortgage banking income
Derivative Financial Instruments
Gain (loss)	$ (232)	$ 209	$ 155