Investment Securities - Amortized Cost and Estimated Fair Value of Held to Maturity Securities and Available for Sale Securities by Contractual Maturity (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Securities Available-for-Sale
Total Amortized Cost	$ 382,069	$ 414,119
Total Gross Unrealized Gains	11,941	12,423
Total Gross Unrealized Losses	(456)	(1,181)
Total Fair Value	393,554	425,361
U.S. treasuries [Member]
Securities Available-for-Sale
Available-for-Sale Securities, Amortized Cost Within 1 year		2,525
Available-for-Sale Securities, Gross Unrealized Gains Within 1 year
Available-for-Sale Securities, Gross Unrealized Losses Within 1 year
Available-for-Sale Securities, Fair Value Within 1 year		2,525
Available-for-Sale Securities, Total Amortized Cost		2,525
Total Gross Unrealized Gains
Total Gross Unrealized Losses
Available-for-Sale Securities, Total Fair Value		2,525
U.S. government corporations and agencies [Member]
Securities Available-for-Sale
Available-for-Sale Securities, Amortized Cost Within 1 year	6,540	10,009
Available-for-Sale Securities, Gross Unrealized Gains Within 1 year	47	77
Available-for-Sale Securities, Gross Unrealized Losses Within 1 year
Available-for-Sale Securities, Fair Value Within 1 year	6,587	10,086
Available-for-Sale Securities, Amortized Cost After 1 to 5 years	126,300	143,189
Available-for-Sale Securities, Gross Unrealized Gains After 1 year to 5 years	1,173	1,022
Available-for-Sale Securities, Gross Unrealized Losses After 1 year to 5 years		(33)
Available-for-Sale Securities, Fair Value After 1 year to 5 years	127,473	144,178
Available-for-Sale Securities, Total Amortized Cost	132,840	153,198
Total Gross Unrealized Gains	1,220	1,099
Total Gross Unrealized Losses		(33)
Available-for-Sale Securities, Total Fair Value	134,060	154,264
State and political subdivisions [Member]
Securities Available-for-Sale
Available-for-Sale Securities, Amortized Cost Within 1 year		752
Available-for-Sale Securities, Gross Unrealized Gains Within 1 year		5
Available-for-Sale Securities, Gross Unrealized Losses Within 1 year
Available-for-Sale Securities, Fair Value Within 1 year		757
Available-for-Sale Securities, Amortized Cost After 1 to 5 years	8,441	10,082
Available-for-Sale Securities, Gross Unrealized Gains After 1 year to 5 years	251	308
Available-for-Sale Securities, Gross Unrealized Losses After 1 year to 5 years	(15)	(16)
Available-for-Sale Securities, Fair Value After 1 year to 5 years	8,677	10,374
Available-for-Sale Securities, Amortized Cost After 5 to 10 years	26,850	11,846
Available-for-Sale Securities, Gross Unrealized Gains After 5 to 10 years	1,029	664
Available-for-Sale Securities, Gross Unrealized Losses After 5 to 10 years	(92)	(3)
Available-for-Sale Securities, Fair Value After 5 to 10 years	27,787	12,507
Available-for-Sale Securities, Amortized Cost Over 10 years	79,808	87,896
Available-for-Sale Securities, Gross Unrealized Gains Over 10 years	4,872	5,472
Available-for-Sale Securities, Gross Unrealized Losses Over 10 years		(1)
Available-for-Sale Securities, Fair Value Over 10 years	84,680	93,367
Available-for-Sale Securities, Total Amortized Cost	115,099	110,576
Total Gross Unrealized Gains	6,152	6,449
Total Gross Unrealized Losses	(107)	(20)
Available-for-Sale Securities, Total Fair Value	121,144	117,005
Residential mortgage-backed securities [Member]
Securities Available-for-Sale
Available-for-Sale Securities, Amortized Cost After 5 to 10 years	17,969	20,745
Available-for-Sale Securities, Gross Unrealized Gains After 5 to 10 years	801	743
Available-for-Sale Securities, Gross Unrealized Losses After 5 to 10 years
Available-for-Sale Securities, Fair Value After 5 to 10 years	18,770	21,488
Available-for-Sale Securities, Amortized Cost Over 10 years	78,487	55,328
Available-for-Sale Securities, Gross Unrealized Gains Over 10 years	2,532	2,665
Available-for-Sale Securities, Gross Unrealized Losses Over 10 years		(680)
Available-for-Sale Securities, Fair Value Over 10 years	81,019	57,313
Available-for-Sale Securities, Total Amortized Cost	96,456	76,073
Total Gross Unrealized Gains	3,333	3,408
Total Gross Unrealized Losses		(680)
Available-for-Sale Securities, Total Fair Value	99,789	78,801
Commercial mortgage obligations [Member]
Securities Available-for-Sale
Available-for-Sale Securities, Amortized Cost After 5 to 10 years	1,983	5,547
Available-for-Sale Securities, Gross Unrealized Gains After 5 to 10 years	34	124
Available-for-Sale Securities, Gross Unrealized Losses After 5 to 10 years
Available-for-Sale Securities, Fair Value After 5 to 10 years	2,017	5,671
Available-for-Sale Securities, Amortized Cost Over 10 years	24,260	54,994
Available-for-Sale Securities, Gross Unrealized Gains Over 10 years	505	799
Available-for-Sale Securities, Gross Unrealized Losses Over 10 years
Available-for-Sale Securities, Fair Value Over 10 years	24,765	55,793
Available-for-Sale Securities, Total Amortized Cost	26,243	60,541
Total Gross Unrealized Gains	539	923
Total Gross Unrealized Losses
Available-for-Sale Securities, Total Fair Value	26,782	61,464
Corporate bonds [Member]
Securities Available-for-Sale
Available-for-Sale Securities, Amortized Cost After 1 to 5 years	4,992	4,991
Available-for-Sale Securities, Gross Unrealized Gains After 1 year to 5 years
Available-for-Sale Securities, Gross Unrealized Losses After 1 year to 5 years	(35)	(224)
Available-for-Sale Securities, Fair Value After 1 year to 5 years	4,957	4,767
Available-for-Sale Securities, Total Amortized Cost	4,992	4,991
Total Gross Unrealized Gains
Total Gross Unrealized Losses	(35)	(224)
Available-for-Sale Securities, Total Fair Value	4,957	4,767
Money market mutual funds [Member]
Securities Available-for-Sale
Available-for-Sale Securities, Amortized Cost Within 1 year	4,147	3,851
Available-for-Sale Securities, Gross Unrealized Gains Within 1 year
Available-for-Sale Securities, Gross Unrealized Losses Within 1 year
Available-for-Sale Securities, Fair Value Within 1 year	4,147	3,851
Available-for-Sale Securities, Total Amortized Cost	4,147	3,851
Total Gross Unrealized Gains
Total Gross Unrealized Losses
Available-for-Sale Securities, Total Fair Value	4,147	3,851
Equity securities [Member]
Securities Available-for-Sale
Available-for-Sale Securities Equity, No stated maturity Amortized Cost	2,292	2,364
Available-for-Sale Securities Equity, No stated maturity Gross Unrealized Gains	697	544
Available For Sale Securities Equity No stated maturity Gross Unrealized Losses	(314)	(224)
Available-for-Sale Securities Equity, No stated maturity Fair Value	2,675	2,684
Available-for-Sale Securities Equity, Total Amortized Cost	2,292	2,364
Available-for-Sale Securities Equity, Total Gross Unrealized Gains	697	544
Available-for-Sale Securities Equity, Total Gross Unrealized Losses	(314)	(224)
Available-for-Sale Securities Equity, Total Fair Value	2,675	2,684
Corporate bonds [Member]
Securities Held-to-Maturity
Held-to-Maturity, Amortized Cost	45,538	45,804
Held-to-Maturity, Gross Unrealized Gains	776	154
Held-to-Maturity, Gross Unrealized Losses	(18)	(319)
Held-to-Maturity, Fair Value	46,296	45,639
Held-to-Maturity After 1 year to 5 years, Amortized Cost	45,538	45,804
Held-to-Maturity After 1 year to 5 years, Gross Unrealized Gains	776	154
Held-to-Maturity After 1 year to 5 years, Gross Unrealized Losses	(18)	(319)
Held-to-Maturity After 1 year to 5 years, Fair Value	$ 46,296	$ 45,639