Loans (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Summary of nonperforming loans
Total nonperforming TDRs	$ 42,172	$ 44,452	$ 39,724
Total loans	3,962,342	3,831,285	3,748,010
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	23,773	19,440	17,568
Total loans	2,129,234	2,085,325	2,050,361
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	18,399	25,012	22,156
Total loans	1,833,108	1,745,960	1,697,649
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	74,456	78,394	105,350
Total accruing loans contractually past due 90 days or more as to interest or principal payments	2,566	3,817	3,744
Total nonperforming TDRs	15,789	24,058	26,835
Total loans	92,811	106,269	135,929
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	11,691	14,675	15,443
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	4,098	9,383	11,392
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	12,673	10,726	14,386
Total accruing loans contractually past due 90 days or more as to interest or principal payments	300	1,381	629
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	41,691	44,438	57,324
Total accruing loans contractually past due 90 days or more as to interest or principal payments	269	374	143
Nonperforming [Member] | Real estate construction and land development [Member]
Summary of nonperforming loans
Total nonaccrual loans	3,485	6,190	8,933
Total accruing loans contractually past due 90 days or more as to interest or principal payments		287
Nonperforming [Member] | Real estate residential [Member]
Summary of nonperforming loans
Total nonaccrual loans	12,613	12,573	17,809
Total accruing loans contractually past due 90 days or more as to interest or principal payments	840	752	1,729
Nonperforming [Member] | Consumer installment and home equity [Member]
Summary of nonperforming loans
Total nonaccrual loans	3,994	4,467	6,898
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 1,157	$ 1,023	$ 1,243