Borrowings - Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Long-term borrowings
2017	$ 2,500
2018	7,000
2019	82,529
2021	7,500
Thereafter	22,500
Long-term debt	122,029	$ 127,029
Fixed Rate
Long-term borrowings
2017	2,500
2018	7,000
2019	7,500
Long-term debt	17,000
Floating Rate
Long-term borrowings
2019	75,029
2021	7,500
Thereafter	22,500
Long-term debt	$ 105,029