Securities (Securities with Unrealized Losses, Presented by Length of Time Securities Have Been in Continuous Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	$ 298,713	$ 403,858
Less than 12 Months Unrealized Loss	(7,640)	(13,850)
12 Months or More Fair Value	79,065	1,735
12 Months or More Unrealized Loss	(3,649)	(88)
Total Fair Value	377,778	405,593
Total Unrealized Loss	(11,289)	(13,938)
U.S. Treasury and Agency Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	19,129	18,952
Less than 12 Months Unrealized Loss	(871)	(1,048)
12 Months or More Fair Value	0	0
12 Months or More Unrealized Loss	0	0
Total Fair Value	19,129	18,952
Total Unrealized Loss	(871)	(1,048)
Obligations of State and Political Subdivisions [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	15,580	38,878
Less than 12 Months Unrealized Loss	(268)	(899)
12 Months or More Fair Value	700	0
12 Months or More Unrealized Loss	(56)	0
Total Fair Value	16,280	38,878
Total Unrealized Loss	(324)	(899)
Mortgage-backed Securities - Residential [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	264,004	346,028
Less than 12 Months Unrealized Loss	(6,501)	(11,903)
12 Months or More Fair Value	78,365	1,735
12 Months or More Unrealized Loss	(3,593)	(88)
Total Fair Value	342,369	347,763
Total Unrealized Loss	(10,094)	(11,991)
Equity Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	0	0
Less than 12 Months Unrealized Loss	0	0
12 Months or More Fair Value	0	0
12 Months or More Unrealized Loss	0	0
Total Fair Value	0	0
Total Unrealized Loss	$ 0	$ 0