Short and Long-Term Funding (Components of Short-term and Long-term Funding) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Short-term Funding [Abstract]
Federal funds purchased	$ 13,090	$ 19,710
Securities sold under agreements to repurchase	114,008	91,941
Federal funds purchased and securities sold under agreements to repurchase	127,098	111,651
Commercial paper	32,019	45,423
Total short-term funding	159,117	157,074
Long-Term Funding
Corporation subordinated notes, at par, due 2025	250,000	250,000
Other long-term funding and capitalized costs	(3,993)	(4,389)
Total long-term funding	796,007	795,611
Long-term Funding
Total short and long-term funding, excluding FHLB advances	955,123	952,685
FHLB Advances
Short-term FHLB advances	20,000	900,000
Long-term FHLB advances	2,924,769	2,674,371
Total FHLB advances	2,944,769	3,574,371
Total short and long-term funding, excluding FHLB advances	3,899,893	4,527,056
Corporation senior notes [Member]
Long-Term Funding
Senior notes, at par	250,000	250,000
Bank senior notes [Member]
Long-Term Funding
Senior notes, at par	$ 300,000	$ 300,000