Loans (Summary of Loans) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Summary of loans under portfolio
Commercial loan	$ 2,445,787	$ 2,264,820	$ 2,159,893
Consumer loan	2,076,884	1,902,915	1,859,266
Total loans	4,522,671	4,167,735	4,019,159
Commercial [Member]
Summary of loans under portfolio
Commercial loan	1,128,122	1,002,722	951,938
Real estate commercial [Member]
Summary of loans under portfolio
Commercial loan	1,215,631	1,161,861	1,117,073
Real estate construction [Member]
Summary of loans under portfolio
Commercial loan	78,361	62,689	56,071
Land development [Member]
Summary of loans under portfolio
Commercial loan	23,673	37,548	34,811
Real estate residential [Member]
Summary of loans under portfolio
Consumer loan	942,777	883,835	880,295
Consumer installment [Member]
Summary of loans under portfolio
Consumer loan	622,040	546,036	538,412
Home equity [Member]
Summary of loans under portfolio
Consumer loan	$ 512,067	$ 473,044	$ 440,559