Loans and Allowance for Loan Losses (Details 5) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Internal loan grading by class of loans
Total loans	$ 3,116,096	$ 3,013,498	$ 2,984,114
Grade 1 [Member]
Internal loan grading by class of loans
Total loans	2,709,926		2,596,700
Grade 2 [Member]
Internal loan grading by class of loans
Total loans	327,755		289,865
Grade 3 [Member]
Internal loan grading by class of loans
Total loans	56,548		67,427
Grade 4 [Member]
Internal loan grading by class of loans
Total loans	21,826		30,025
Grade 5 [Member]
Internal loan grading by class of loans
Total loans	41		97
Non-residential real estate [Member]
Internal loan grading by class of loans
Total loans	1,149,570		1,029,549
Non-residential real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	984,606		881,622
Non-residential real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	127,768		107,228
Non-residential real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	27,523		32,223
Non-residential real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	9,673		8,476
Residential real estate [Member]
Internal loan grading by class of loans
Total loans	737,798		695,916
Residential real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	636,564		602,621
Residential real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	81,970		72,095
Residential real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	14,667		14,805
Residential real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	4,597		6,395
Non-consumer non-real estate [Member]
Internal loan grading by class of loans
Total loans	733,906		692,510
Non-consumer non-real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	644,066		620,123
Non-consumer non-real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	80,863		63,375
Non-consumer non-real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	6,500		7,881
Non-consumer non-real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	2,477		1,131
Consumer non-real estate [Member]
Internal loan grading by class of loans
Total loans	207,743		201,632
Consumer non-real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	195,242		189,895
Consumer non-real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	10,185		8,950
Consumer non-real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	1,965		2,380
Consumer non-real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	349		407
Consumer non-real estate [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans	2
Other loans [Member]
Internal loan grading by class of loans
Total loans	150,482		158,543
Other loans [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	146,037		151,336
Other loans [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	2,726		2,608
Other loans [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	887		1,874
Other loans [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	832		2,725
Acquired loans [Member]
Internal loan grading by class of loans
Total loans	136,597		205,964
Acquired loans [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	103,411		151,103
Acquired loans [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	24,243		35,609
Acquired loans [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	5,006		8,264
Acquired loans [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	3,898		10,891
Acquired loans [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans	$ 39		$ 97