Short-term borrowings (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary of securities sold under agreements to repurchase
Average balance during the year	$ 3,425	$ 3,343	$ 51,694
Average interest rate during the year	0.66%	1.36%	0.67%
Maximum month-end balance during the year	$ 5,150	$ 5,505	$ 87,163
Weighted average year-end interest rate	0.66%	1.36%	0.67%
Balance at year-end	$ 2,171	$ 1,700	$ 4,409