Short-term Funding, Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Abstract]
Federal funds purchased	$ 208,150	$ 47,870
Securities sold under agreements to repurchase	300,197	383,568
Federal funds purchased and securities sold under agreements to repurchase	508,347	431,438
FHLB advances	482,000	335,000
Commercial paper	101,688	67,978
Other short-term funding	583,688	402,978
Total short-term funding	$ 1,092,035	$ 834,416