Borrowed Funds - Short-Term Credit Lines Available for Use (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
FRB's Discount Window Primary Credit Program
Line of Credit Facility [Line Items]
Amount outstanding	$ 864,867	$ 874,256
Available federal funds lines
Line of Credit Facility [Line Items]
Amount outstanding	844,000	718,000
Correspondent bank line of credit
Line of Credit Facility [Line Items]
Amount outstanding	$ 50,000	$ 50,000