Fair Value Disclosures - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Available-for-sale securities:
Total available-for-sale securities	$ 393,554	$ 425,361	[1]
Liabilities:
Contingent consideration liability	842
Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Total available-for-sale securities	393,554	425,361
Total assets	395,580	426,440
Liabilities:
Total Liabilities	3,078	1,737
Fair Value, Measurements, Recurring [Member] | U.S. government treasuries [Member]
Available-for-sale securities:
Total available-for-sale securities		2,525
Fair Value, Measurements, Recurring [Member] | U.S government corporations and agencies [Member]
Available-for-sale securities:
Total available-for-sale securities	134,060	154,264
Fair Value, Measurements, Recurring [Member] | State and political subdivisions [Member]
Available-for-sale securities:
Total available-for-sale securities	121,144	117,005
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed securities [Member]
Available-for-sale securities:
Total available-for-sale securities	99,789	78,801
Fair Value, Measurements, Recurring [Member] | Commercial mortgage obligations [Member]
Available-for-sale securities:
Total available-for-sale securities	26,782	61,464
Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member]
Available-for-sale securities:
Total available-for-sale securities	4,957	4,767
Fair Value, Measurements, Recurring [Member] | Money market mutual funds [Member]
Available-for-sale securities:
Total available-for-sale securities	4,147	3,851
Fair Value, Measurements, Recurring [Member] | Equity securities [Member]
Available-for-sale securities:
Total available-for-sale securities	2,675	2,684
Fair Value, Measurements, Recurring [Member] | Interest rate locks with customers [Member]
Available-for-sale securities:
Derivative assets	2,026	1,079
Fair Value, Measurements, Recurring [Member] | Interest rate swap [Member]
Liabilities:
Liabilities	1,824	1,435
Fair Value, Measurements, Recurring [Member] | Forward loan commitments [Member]
Liabilities:
Liabilities	412	302
Fair Value, Measurements, Recurring [Member] | Contingent Consideration Liability [Member]
Liabilities:
Contingent consideration liability	842
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Available-for-sale securities:
Total available-for-sale securities	6,822	9,060
Total assets	6,822	9,060
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. government treasuries [Member]
Available-for-sale securities:
Total available-for-sale securities		2,525
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Money market mutual funds [Member]
Available-for-sale securities:
Total available-for-sale securities	4,147	3,851
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Equity securities [Member]
Available-for-sale securities:
Total available-for-sale securities	2,675	2,684
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Available-for-sale securities:
Total available-for-sale securities	386,732	416,301
Total assets	388,758	417,380
Liabilities:
Total Liabilities	2,236	1,737
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S government corporations and agencies [Member]
Available-for-sale securities:
Total available-for-sale securities	134,060	154,264
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | State and political subdivisions [Member]
Available-for-sale securities:
Total available-for-sale securities	121,144	117,005
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Residential mortgage-backed securities [Member]
Available-for-sale securities:
Total available-for-sale securities	99,789	78,801
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial mortgage obligations [Member]
Available-for-sale securities:
Total available-for-sale securities	26,782	61,464
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate bonds [Member]
Available-for-sale securities:
Total available-for-sale securities	4,957	4,767
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest rate locks with customers [Member]
Available-for-sale securities:
Derivative assets	2,026	1,079
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest rate swap [Member]
Liabilities:
Liabilities	1,824	1,435
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Forward loan commitments [Member]
Liabilities:
Liabilities	412	302
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Liabilities:
Total Liabilities	842
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Contingent Consideration Liability [Member]
Liabilities:
Contingent consideration liability	$ 842

[1] Note: The consolidated balance sheet at December 31, 2011 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U. S. generally accepted accounting principles for complete financial statements. Certain amounts have been reclassified to conform to the current-year presentation. See accompanying notes to the unaudited consolidated financial statements.