Short and Long-Term Funding, FHLB Advances (Components of Short-term and Long-term Funding) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Short-term Funding [Abstract]
Federal funds purchased	$ 24,480	$ 362,000
Securities sold under agreements to repurchase	108,527	71,097
Federal funds purchased and securities sold under agreements to repurchase	133,007	433,097
Commercial paper	33,647	32,016
Total short-term funding	166,654	465,113
Long-Term Funding
Corporation subordinated notes, at par, due 2025	250,000	250,000
Finance Lease, Liability	2,210	2,209
Capitalized costs	(2,565)	(2,866)
Total long-term funding	549,644	549,343
Total short and long-term funding, excluding FHLB advances	716,299	1,014,456
FHLB Advances
Short-term FHLB advances	550,000	520,000
Long-term FHLB advances	2,664,194	2,660,967
Total FHLB advances	3,214,194	3,180,967
Total short and long-term funding	3,930,493	4,195,422
Bank senior notes, at par, due 2021
Long-Term Funding
Senior notes	$ 300,000	$ 300,000