Securities (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Available For Sale Securities, Amortized Cost
Total	$ 1,435,118	$ 1,395,983
Available For Sale Securities, Fair value
Total	1,448,971	1,400,809
Total debt securities [Member]
Available For Sale Securities, Amortized Cost
Due in one year or less	68,446	67,281
Due after one year through five years	391,117	342,548
Due after five years through ten years	173,150	199,724
Due after ten years	15,961	17,037
Total	648,674	626,590
Available For Sale Securities, Fair value
Due in one year or less	69,829	68,350
Due after one year through five years	398,772	347,230
Due after five years through ten years	174,819	199,276
Due after ten years	15,619	16,636
Total	659,039	631,492
Mortgage-backed securities [Member]
Available For Sale Securities, Amortized Cost
Total	786,444	769,393
Available For Sale Securities, Fair value
Total	$ 789,932	$ 769,317