Short and Long-Term Funding, FHLB Advances (Components of Short-term and Long-term Funding) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Short-term Funding [Abstract]
Federal funds purchased	$ 7,575	$ 362,000
Securities sold under agreements to repurchase	147,754	71,097
Federal funds purchased and securities sold under agreements to repurchase	155,329	433,097
Commercial paper	50,987	32,016
Total short-term funding	206,316	465,113
Long-Term Funding
Corporation subordinated notes, at par, due 2025	250,000	250,000
PPPLF	1,022,217	0
Finance lease liability	1,165	2,209
Capitalized costs	(1,964)	(2,866)
Total long-term funding	1,571,418	549,343
Total short and long-term funding, excluding FHLB advances	1,777,735	1,014,456
FHLB Advances
Short-term FHLB advances	0	520,000
Long-term FHLB advances	1,706,763	2,660,967
FHLB advances	1,706,763	3,180,967
Total short and long-term funding	3,484,498	4,195,422
Bank senior notes, at par, due 2021
Long-Term Funding
Senior notes	$ 300,000	$ 300,000