Borrowings (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Short-term borrowings, amount	$ 30,000	$ 42,040
Short-term borrowings, interest rate	1.18%	0.42%
Pledged financial instruments, securities for federal home loan bank	$ 219,000	$ 229,000
FHLB short-term advance [Member]
Short-term Debt [Line Items]
Short-term borrowings, amount	$ 30,000	$ 25,000
Short-term borrowings, interest rate	1.18%	0.63%
Repurchase agreements [Member]
Short-term Debt [Line Items]
Short-term borrowings, amount	$ 0	$ 17,040
Short-term borrowings, interest rate	0.00%	0.10%