Investment Securities (Details 3) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Other investment securities
Amortized Cost	$ 13,386	$ 9,768	$ 7,996
Fair Value	13,386	9,768	7,996
Amortized Cost
Due in one year or less	750
Due after one year through five years	1,075
Due after five years through ten years	8,658
Due after ten years	1,943
Total	12,426
Fair Value
Due in one year or less	762
Due after one year through five years	1,123
Due after five years through ten years	9,042
Due after ten years	2,065
Fair Value	12,992	16,553	17,750
Amortized Cost
Due in one year or less	5,411
Due after one year through five years	13,255
Due after five years through ten years	221,162
Due after ten years	391,128
Total	630,956	520,826	462,253
Fair Value
Due in one year or less	5,437
Due after one year through five years	13,570
Due after five years through ten years	219,392
Due after ten years	388,399
Fair Value	626,798	534,883	476,023
Federal Home Loan Bank stock
Other investment securities
Amortized Cost	10,352	8,126	6,664
Fair Value	10,352	8,126	6,664
Investment in unconsolidated subsidiaries
Other investment securities
Amortized Cost	3,034	1,642	1,332
Fair Value	$ 3,034	$ 1,642	$ 1,332