Borrowings - Short-term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Borrowings
Balance outstanding at year end	$ 34,735	$ 20,455
Maximum balance at any month end during the year	38,197	60,481
Average balance for the year	$ 27,360	$ 22,737
Weighted average rate for the year (as a percent)	0.47%	0.54%
Weighted average rate on borrowings at year end	0.48%	0.49%
Estimated fair value at year end	$ 34,735	$ 20,455