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
Amount
At period-end	$ 298,741	$ 270,649
Rate
Repurchase agreement	242,200	205,300
Carrying amount of the securities pledged to collateralize repurchase agreements	242,200	205,300
Federal funds purchased and securities sold under repurchase agreements
Amount
At period-end	298,741	270,649	$ 286,857
Average for the year	282,172	312,768	325,713
Maximum month-end balance	$ 321,833	$ 362,047	$ 401,786
Rate
At period-end (as a percent)	0.90%	1.08%	0.45%
Average for the year (as a percent)	0.93%	0.75%	0.33%
Federal funds purchased and securities sold under repurchase agreements | Minimum
Information concerning federal funds purchased and securities sold under repurchase agreements
Maturity period from the transaction date	1 day
Federal funds purchased and securities sold under repurchase agreements | Maximum
Information concerning federal funds purchased and securities sold under repurchase agreements
Maturity period from the transaction date	3 days
Maturity period as per policies	9 months