Short-term borrowings (Details) - Repurchase agreement - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Sale of repurchase agreement [Line items]
Total repurchase agreements	$ 88,767	$ 75,482
U.S. Treasury and U.S. government sponsored entities
Sale of repurchase agreement [Line items]
Total repurchase agreements	9,425	5,276
State and political subdivisions
Sale of repurchase agreement [Line items]
Total repurchase agreements	2,697	2,640
Mortgage-backed securities - residential
Sale of repurchase agreement [Line items]
Total repurchase agreements	67,635	60,391
Collateralized mortgage obligations - residential
Sale of repurchase agreement [Line items]
Total repurchase agreements	$ 9,010	$ 7,175