Securities, Temporarily Impaired Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Security	Mar. 31, 2012 Security	Dec. 31, 2012
Temporarily impaired securities with gross unrealized losses and fair value [Abstract]
Less Than 12 Months, Fair Value	$ 117,252		$ 53,709
Less Than 12 Months, Unrealized Loss	2,401		838
12 Months or More, Fair Value	841		615
12 Months or More, Unrealized Loss	138		175
Number of temporarily impaired securities	137	4
Fair Value of temporarily impaired securities	118,093	841
Unrealized loss on securities	2,539	137
U.S. Government Agencies and Corporations [Member]
Temporarily impaired securities with gross unrealized losses and fair value [Abstract]
Less Than 12 Months, Fair Value	85,100		44,351
Less Than 12 Months, Unrealized Loss	1,222		622
12 Months or More, Fair Value	0		0
12 Months or More, Unrealized Loss	0		0
State and Political Subdivisions [Member]
Temporarily impaired securities with gross unrealized losses and fair value [Abstract]
Less Than 12 Months, Fair Value	28,178		9,358
Less Than 12 Months, Unrealized Loss	1,127		216
12 Months or More, Fair Value	481		482
12 Months or More, Unrealized Loss	4		3
Corporate Debt Securities [Member]
Temporarily impaired securities with gross unrealized losses and fair value [Abstract]
Less Than 12 Months, Fair Value	3,974
Less Than 12 Months, Unrealized Loss	52
12 Months or More, Fair Value	0
12 Months or More, Unrealized Loss	0
Other [Member]
Temporarily impaired securities with gross unrealized losses and fair value [Abstract]
Less Than 12 Months, Fair Value	0		0
Less Than 12 Months, Unrealized Loss	0		0
12 Months or More, Fair Value	360		133
12 Months or More, Unrealized Loss	$ 134		$ 172