Loans (Summary of Loans) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Summary of loans under portfolio
Commercial loan	$ 2,364,870	$ 2,264,820	$ 2,129,234
Consumer loan	1,971,001	1,902,915	1,833,108
Total loans	4,335,871	4,167,735	3,962,342
Commercial [Member]
Summary of loans under portfolio
Commercial loan	1,091,894	1,002,722	915,352
Real estate commercial [Member]
Summary of loans under portfolio
Commercial loan	1,172,347	1,161,861	1,119,655
Real estate construction [Member]
Summary of loans under portfolio
Commercial loan	73,448	62,689	54,538
Land development [Member]
Summary of loans under portfolio
Commercial loan	27,181	37,548	39,689
Real estate residential [Member]
Summary of loans under portfolio
Consumer loan	898,816	883,835	873,214
Consumer installment [Member]
Summary of loans under portfolio
Consumer loan	577,241	546,036	535,283
Home equity [Member]
Summary of loans under portfolio
Consumer loan	$ 494,944	$ 473,044	$ 424,611