Securities Sold Under Agreements to Repurchase and Other Borrowings (Additional Information for Short-term Borrowings) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	$ 1,009,662	$ 1,076,160
Federal funds purchased	322,000	0
At end of year [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	359,662	326,160	290,856
Securities sold under agreements to repurchase, Rate	0.16%	0.15%	0.20%
Federal funds purchased	322,000	0	223,000
Federal funds purchased, Rate	0.20%	0.00%	0.12%
Average during year [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	316,560	306,294	310,355
Securities sold under agreements to repurchase, Rate	0.15%	0.18%	0.22%
Federal funds purchased	255,689	173,690	122,656
Federal funds purchased, Rate	0.18%	0.17%	0.14%
Highest month-end balance during year [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities sold under agreements to repurchase	372,922	357,396	342,795
Securities sold under agreements to repurchase, Rate	0.00%	0.00%	0.00%
Federal funds purchased	$ 398,000	$ 255,200	$ 282,000
Federal funds purchased, Rate	0.00%	0.00%	0.00%