Loans and Allowance for Loan Losses (Details 5) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Internal loan grading by class of loans
Total loans	$ 3,219,967	$ 3,242,427	$ 3,049,376
Grade 1 [Member]
Internal loan grading by class of loans
Total loans	2,773,325		2,645,309
Grade 2 [Member]
Internal loan grading by class of loans
Total loans	375,201		318,990
Grade 3 [Member]
Internal loan grading by class of loans
Total loans	51,969		64,538
Grade 4 [Member]
Internal loan grading by class of loans
Total loans	19,468		20,539
Grade 5 [Member]
Internal loan grading by class of loans
Total loans	4
Non-residential real estate [Member]
Internal loan grading by class of loans
Total loans	1,244,042		1,101,914
Non-residential real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	1,043,069		951,016
Non-residential real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	165,295		112,408
Non-residential real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	25,994		28,721
Non-residential real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	9,684		9,769
Non-residential real estate [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans
Residential real estate [Member]
Internal loan grading by class of loans
Total loans	773,793		696,070
Residential real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	670,352		591,818
Residential real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	84,644		83,250
Residential real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	14,140		15,579
Residential real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	4,657		5,423
Residential real estate [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans
Non-consumer non-real estate [Member]
Internal loan grading by class of loans
Total loans	750,601		725,088
Non-consumer non-real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	647,162		636,582
Non-consumer non-real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	97,110		79,548
Non-consumer non-real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	4,800		7,480
Non-consumer non-real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	1,529		1,478
Non-consumer non-real estate [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans
Consumer non-real estate [Member]
Internal loan grading by class of loans
Total loans	211,320		200,208
Consumer non-real estate [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	198,107		187,999
Consumer non-real estate [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	10,912		9,690
Consumer non-real estate [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	1,923		2,132
Consumer non-real estate [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	374		387
Consumer non-real estate [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans	4
Other loans [Member]
Internal loan grading by class of loans
Total loans	144,026		163,488
Other loans [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	139,696		158,729
Other loans [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	2,304		2,775
Other loans [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	1,103		1,725
Other loans [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	923		259
Other loans [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans
Acquired loans [Member]
Internal loan grading by class of loans
Total loans	96,185		162,608
Acquired loans [Member] | Grade 1 [Member]
Internal loan grading by class of loans
Total loans	74,939		119,165
Acquired loans [Member] | Grade 2 [Member]
Internal loan grading by class of loans
Total loans	14,936		31,319
Acquired loans [Member] | Grade 3 [Member]
Internal loan grading by class of loans
Total loans	4,009		8,901
Acquired loans [Member] | Grade 4 [Member]
Internal loan grading by class of loans
Total loans	2,301		3,223
Acquired loans [Member] | Grade 5 [Member]
Internal loan grading by class of loans
Total loans