Investment Securities (Details 3) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	$ 141,107	$ 288,058	$ 242,944
Less Than 12 Months, Gross Unrealized Losses	2,536	1,306	2,291
12 Months or More, Fair Value	107,211	97,896	52,599
12 Months or More, Gross Unrealized Losses	5,661	7,107	6,382
Total, Fair Value	248,318	385,954	295,543
Total, Gross Unrealized Losses	8,197	8,413	8,673
Government sponsored agencies [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	39,729	9,883	28,763
Less Than 12 Months, Gross Unrealized Losses	248	36	59
12 Months or More, Fair Value	8,808	9,632	2,753
12 Months or More, Gross Unrealized Losses	18	11	2
Total, Fair Value	48,537	19,515	31,516
Total, Gross Unrealized Losses	266	47	61
State and political subdivisions [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	69,841	0	38,661
Less Than 12 Months, Gross Unrealized Losses	1,711	0	874
12 Months or More, Fair Value	1,533	31,706	7,544
12 Months or More, Gross Unrealized Losses	8	342	134
Total, Fair Value	71,374	31,706	46,205
Total, Gross Unrealized Losses	1,719	342	1,008
Residential mortgage-backed securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	32	27,367	29,560
Less Than 12 Months, Gross Unrealized Losses	1	152	343
12 Months or More, Fair Value	19,704	19,018	19,206
12 Months or More, Gross Unrealized Losses	15	149	103
Total, Fair Value	19,736	46,385	48,766
Total, Gross Unrealized Losses	16	301	446
Collateralized Mortgage Obligations [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	12,036	200,218	108,302
Less Than 12 Months, Gross Unrealized Losses	45	703	367
12 Months or More, Fair Value	47,066	18,176	16,164
12 Months or More, Gross Unrealized Losses	229	129	77
Total, Fair Value	59,102	218,394	124,466
Total, Gross Unrealized Losses	274	832	444
Corporate bonds [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	19,469	50,590	37,658
Less Than 12 Months, Gross Unrealized Losses	531	415	648
12 Months or More, Fair Value	24,900	14,580	2,467
12 Months or More, Gross Unrealized Losses	91	420	31
Total, Fair Value	44,369	65,170	40,125
Total, Gross Unrealized Losses	622	835	679
Trust Preferred Securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	0	0	0
Less Than 12 Months, Gross Unrealized Losses	0	0	0
12 Months or More, Fair Value	5,200	4,465	4,465
12 Months or More, Gross Unrealized Losses	5,300	6,035	6,035
Total, Fair Value	5,200	4,465	4,465
Total, Gross Unrealized Losses	5,300	6,035	6,035
Preferred stock [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value		0
Less Than 12 Months, Gross Unrealized Losses		0
12 Months or More, Fair Value		319
12 Months or More, Gross Unrealized Losses		21
Total, Fair Value		319
Total, Gross Unrealized Losses		$ 21