Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Repurchase agreements	$ 251,065	$ 251,225
Federal funds purchased	4,816	3,596
Total short-term debt	255,881	$ 254,821
Maximum balance for repurchase agreements at any month-end	$ 264,500
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Average interest rate	0.54%
Repurchase Agreements [Member]
Short-term Debt [Line Items]
Average interest rate	0.51%
Average balance of repurchase agreements	$ 256,600