Borrowings - Federal Funds Purchased and Securities Sold Under Agreements to Repurchase (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Maximum amount outstanding at any month end	$ 193,388	$ 341,213	$ 216,094
Weighted average interest rate at end of year	1.17%	1.14%	0.71%
Average amount outstanding	$ 106,142	$ 200,839	$ 171,686
Weighted average interest rate during the year	1.35%	0.90%	0.46%