Loans and Allowance for Loan Losses (Details 5) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Internal loan grading by class of loans
Total loans	$ 3,065,439	$ 3,013,498	$ 2,861,844
Grade 1 [Member]
Internal loan grading by class of loans
Total loans	2,662,879		2,502,004
Grade 2 [Member]
Internal loan grading by class of loans
Total loans	319,097		269,320
Grade 3 [Member]
Internal loan grading by class of loans
Total loans	62,692		69,746
Grade 4 [Member]
Internal loan grading by class of loans
Total loans	20,771		20,676
Grade 5 [Member]
Internal loan grading by class of loans
Total loans			98
Non-residential real estate [Member]
Internal loan grading by class of loans
Total loans	1,141,051		980,702
Non-residential real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	983,946		834,857
Non-residential real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	118,825		103,359
Non-residential real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	28,514		33,446
Non-residential real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	9,766		9,040
Residential real estate [Member]
Internal loan grading by class of loans
Total loans	721,149		689,169
Residential real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	619,115		601,469
Residential real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	81,324		68,651
Residential real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	15,920		12,970
Residential real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	4,790		6,079
Non-consumer non-real estate [Member]
Internal loan grading by class of loans
Total loans	697,416		712,438
Non-consumer non-real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	610,214		638,872
Non-consumer non-real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	78,825		61,481
Non-consumer non-real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	7,211		10,710
Non-consumer non-real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	1,166		1,375
Consumer non-real estate [Member]
Internal loan grading by class of loans
Total loans	200,427		198,578
Consumer non-real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	187,768		189,220
Consumer non-real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	10,204		6,891
Consumer non-real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	2,122		2,172
Consumer non-real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	333		295
Other loans [Member]
Internal loan grading by class of loans
Total loans	155,984		160,237
Other loans [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	151,330		153,104
Other loans [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	2,917		2,463
Other loans [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	1,027		2,050
Other loans [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	710		2,620
Acquired loans [Member]
Internal loan grading by class of loans
Total loans	149,412		120,720
Acquired loans [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	110,506		84,482
Acquired loans [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	27,002		26,475
Acquired loans [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	7,898		8,398
Acquired loans [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	4,006		1,267
Acquired loans [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans			$ 98