Short-term Funding, Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Short-term Debt [Abstract]
Federal funds purchased	$ 47,870	$ 109,770
Securities sold under agreements to repurchase	383,568	384,221
Federal funds purchased and securities sold under agreements to repurchase	431,438	493,991
FHLB advances	335,000	500,000
Commercial paper	67,978	74,297
Other short-term funding	402,978	574,297
Total short-term funding	$ 834,416	$ 1,068,288