Credit Quality (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans
Loans, 30-89 Days Past Due	$ 80,952	$ 100,874
Loans, 90 Days or more Past Due	74,136	77,599
Loans, Total Past Due	155,088	178,473
Loans, Current	6,057,658	6,061,740
Total gross loans	6,212,746	6,240,213
Loans, Recorded Investment >90 Days & Accruing	9,816	16,179
Owner-occupied [Member]
Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans
Loans, 30-89 Days Past Due	4,890	4,625
Loans, 90 Days or more Past Due	3,264	4,707
Loans, Total Past Due	8,154	9,332
Loans, Current	732,219	734,170
Total gross loans	740,373	743,502
Loans, Recorded Investment >90 Days & Accruing	37	1,597
Nonowner-occupied [Member]
Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans
Loans, 30-89 Days Past Due	14,678	16,694
Loans, 90 Days or more Past Due	14,819	13,285
Loans, Total Past Due	29,497	29,979
Loans, Current	1,550,317	1,523,280
Total gross loans	1,579,814	1,553,259
Loans, Recorded Investment >90 Days & Accruing	864	2,233
Other Commercial [Member]
Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans
Loans, 30-89 Days Past Due	5,350	7,131
Loans, 90 Days or more Past Due	13,021	14,153
Loans, Total Past Due	18,371	21,284
Loans, Current	1,162,319	1,190,921
Total gross loans	1,180,690	1,212,205
Loans, Recorded Investment >90 Days & Accruing	310	761
Residential Real Estate [Member]
Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans
Loans, 30-89 Days Past Due	45,241	52,654
Loans, 90 Days or more Past Due	26,204	26,617
Loans, Total Past Due	71,445	79,271
Loans, Current	1,791,361	1,818,387
Total gross loans	1,862,806	1,897,658
Loans, Recorded Investment >90 Days & Accruing	7,196	8,833
Construction & land development [Member]
Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans
Loans, 30-89 Days Past Due	6,523	13,809
Loans, 90 Days or more Past Due	16,408	17,820
Loans, Total Past Due	22,931	31,629
Loans, Current	546,292	518,248
Total gross loans	569,223	549,877
Loans, Recorded Investment >90 Days & Accruing	1,075	1,840
Bankcard [Member]
Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans
Loans, 30-89 Days Past Due	318	222
Loans, 90 Days or more Past Due	120	176
Loans, Total Past Due	438	398
Loans, Current	10,136	11,121
Total gross loans	10,574	11,519
Loans, Recorded Investment >90 Days & Accruing	120	176
Other consumer [Member]
Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans
Loans, 30-89 Days Past Due	3,952	5,739
Loans, 90 Days or more Past Due	300	841
Loans, Total Past Due	4,252	6,580
Loans, Current	265,014	265,613
Total gross loans	269,266	272,193
Loans, Recorded Investment >90 Days & Accruing	$ 214	$ 739