Short and Long-Term Funding (Components of Short-term and Long-term Funding) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Short-Term Funding
Federal funds purchased	$ 177,940	$ 109,770
Securities sold under agreements to repurchase	524,629	384,221
Federal funds purchased and securities sold under agreements to repurchase	702,569	493,991
FHLB advances	260,000	500,000
Commercial paper	59,766	74,297
Other short-term funding	319,766	574,297
Total short-term funding	1,022,335	1,068,288
Long-Term Funding
FHLB advances	1,750,234	3,000,260
Senior notes, at par	680,000	680,000
Subordinated notes, at par	250,000	250,000
Other long-term funding and capitalized costs	(692)	(143)
Total long-term funding	2,679,542	3,930,117
Total short and long-term funding	$ 3,701,877	$ 4,998,405