Short and Long-Term Funding (Components of Short-term and Long-term Funding) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Short-term Funding [Abstract]
Federal funds purchased	$ 220,575	$ 208,150
Securities sold under agreements to repurchase	255,975	300,197
Federal funds purchased and securities sold under agreements to repurchase	476,550	508,347
FHLB advances	520,000	482,000
Commercial paper	68,067	101,688
Other short-term funding	588,067	583,688
Total short-term funding	1,064,617	1,092,035
Long-term Funding
FHLB advances	2,650,172	2,265,188
Senior notes, at par	250,000	250,000
Subordinated notes, at par	250,000	250,000
Other long-term funding and capitalized costs	(2,887)	(3,393)
Total long-term funding	3,147,285	2,761,795
Total short and long-term funding	$ 4,211,902	$ 3,853,830