Investment Securities (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	$ 173,205	$ 288,058	$ 221,786
Less Than 12 Months, Gross Unrealized Losses	2,206	1,306	1,712
12 Months or More, Fair Value	109,603	97,896	51,033
12 Months or More, Gross Unrealized Losses	6,569	7,107	6,115
Total, Fair Value	282,808	385,954	272,819
Total, Gross Unrealized Losses	8,775	8,413	7,827
Government sponsored agencies [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	30,177	9,883	29,311
Less Than 12 Months, Gross Unrealized Losses	61	36	34
12 Months or More, Fair Value	9,516	9,632	2,860
12 Months or More, Gross Unrealized Losses	20	11	2
Total, Fair Value	39,693	19,515	32,171
Total, Gross Unrealized Losses	81	47	36
State and political subdivisions [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	49,355		48,011
Less Than 12 Months, Gross Unrealized Losses	1,100		1,046
12 Months or More, Fair Value	8,258	31,706	12,173
12 Months or More, Gross Unrealized Losses	73	342	183
Total, Fair Value	57,613	31,706	60,184
Total, Gross Unrealized Losses	1,173	342	1,229
Residential mortgage-backed securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	13,038	27,367	25,538
Less Than 12 Months, Gross Unrealized Losses	23	152	185
12 Months or More, Fair Value	19,988	19,018	1,240
12 Months or More, Gross Unrealized Losses	177	149	6
Total, Fair Value	33,026	46,385	26,778
Total, Gross Unrealized Losses	200	301	191
Collateralized Mortgage Obligations [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	30,651	200,218	94,073
Less Than 12 Months, Gross Unrealized Losses	296	703	300
12 Months or More, Fair Value	52,335	18,176	27,617
12 Months or More, Gross Unrealized Losses	306	129	71
Total, Fair Value	82,986	218,394	121,690
Total, Gross Unrealized Losses	602	832	371
Corporate bonds [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	49,984	50,590	24,853
Less Than 12 Months, Gross Unrealized Losses	726	415	147
12 Months or More, Fair Value	14,831	14,580	2,468
12 Months or More, Gross Unrealized Losses	168	420	28
Total, Fair Value	64,815	65,170	27,321
Total, Gross Unrealized Losses	894	835	175
Trust Preferred Securities [Member]
Summary of continuous unrealized loss position of securities
12 Months or More, Fair Value	4,675	4,465	4,675
12 Months or More, Gross Unrealized Losses	5,825	6,035	5,825
Total, Fair Value	4,675	4,465	4,675
Total, Gross Unrealized Losses	5,825	6,035	5,825
Preferred stock [Member]
Summary of continuous unrealized loss position of securities
12 Months or More, Fair Value		319
12 Months or More, Gross Unrealized Losses		21
Total, Fair Value		319
Total, Gross Unrealized Losses		$ 21