Borrowings - Federal Funds Purchased and Securities Sold Under Agreements to Repurchase (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Maximum amount outstanding at any month end	$ 119,609	$ 193,388	$ 341,213
Weighted average interest rate at end of year	0.16%	1.17%	1.14%
Average amount outstanding	$ 84,514	$ 106,142	$ 200,839
Weighted average interest rate during the year	0.33%	1.35%	0.90%