Short and Long-Term Funding, FHLB Advances (Components of Short-term and Long-term Funding) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Short-term Funding [Abstract]
Federal funds purchased	$ 7,450	$ 7,070
Securities sold under agreements to repurchase	131,057	185,901
Federal funds purchased and securities sold under agreements to repurchase	138,507	192,971
Commercial paper	51,171	59,346
Total short-term funding	189,678	252,317
Long-Term Funding
Corporation subordinated notes, at par, due 2025	250,000	250,000
Finance lease liability	1,091	1,128
Capitalized costs	(1,362)	(1,663)
FHLB Advances - long-term
FHLB advances	1,629,966	1,632,723
Total long-term funding	2,179,694	2,182,188
Total short and long-term funding	2,369,372	2,434,505
Bank senior notes, at par, due 2021
Long-Term Funding
Senior notes	$ 300,000	$ 300,000