Borrowings - Federal Funds Purchased, Securities Sold Under Agreements to Repurchase and Short-term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Securities sold under agreements to repurchase
Securities sold under agreements to repurchase	$ 34,864	$ 26,869
Weighted-average interest rate at year-end	0.01%	0.01%
Maximum amount outstanding at any month's end	$ 35,660	$ 34,253
Average amount outstanding during the year	$ 31,076	$ 30,095
Weighted-average interest rate during the year	0.01%	0.21%