Borrowed Funds - Short-term Borrowings and Repurchase Agreements (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Short-term Borrowings from FHLB
Short-term Borrowings and Repurchase Agreements
Balance at end of period	$ 186,772	$ 87,733
Average balance during the period	89,631	137,822
Maximum month-end balance	$ 186,772	$ 210,600
Weighted-average rate during the year	1.10%	0.51%
Weighted-average rate at end of period	1.24%	0.74%
Investment Securities
Short-term Borrowings and Repurchase Agreements
Investment securities held as collateral	$ 23,900	$ 26,000
Repurchase Agreements
Short-term Borrowings and Repurchase Agreements
Balance at end of period	22,194	25,160
Average balance during the period	21,268	27,066
Maximum month-end balance	$ 24,126	$ 29,561
Weighted-average rate during the year	0.34%	0.27%
Weighted-average rate at end of period	0.33%	0.28%