Investment Securities (Summary of Investment Securities with Gross Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	$ 205,142	$ 141,129	$ 154,996
Less Than 12 Months, Gross Unrealized Losses	2,013	2,734	1,420
12 Months or More, Fair Value	45,310	86,618	93,448
12 Months or More, Gross Unrealized Losses	5,068	6,351	6,586
Total, Fair Value	250,452	227,747	248,444
Total, Gross Unrealized Losses	7,081	9,085	8,006
Government sponsored agencies [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	17,281	46,103	19,205
Less Than 12 Months, Gross Unrealized Losses	168	213	54
12 Months or More, Fair Value	0	0	9,897
12 Months or More, Gross Unrealized Losses	0	0	25
Total, Fair Value	17,281	46,103	29,102
Total, Gross Unrealized Losses	168	213	79
State and political subdivisions [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	73,880	70,675	26,775
Less Than 12 Months, Gross Unrealized Losses	1,667	2,257	525
12 Months or More, Fair Value	10,685	8,046	3,956
12 Months or More, Gross Unrealized Losses	219	1,110	24
Total, Fair Value	84,565	78,721	30,731
Total, Gross Unrealized Losses	1,886	3,367	549
Residential mortgage-backed securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	86,179	273	32
Less Than 12 Months, Gross Unrealized Losses	45	1	1
12 Months or More, Fair Value	374	1,305	20,630
12 Months or More, Gross Unrealized Losses	3	8	158
Total, Fair Value	86,553	1,578	20,662
Total, Gross Unrealized Losses	48	9	159
Collateralized Mortgage Obligations [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	27,802	19,331	79,386
Less Than 12 Months, Gross Unrealized Losses	133	10	448
12 Months or More, Fair Value	8,560	36,835	39,597
12 Months or More, Gross Unrealized Losses	37	172	247
Total, Fair Value	36,362	56,166	118,983
Total, Gross Unrealized Losses	170	182	695
Corporate bonds [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	0	4,747	29,598
Less Than 12 Months, Gross Unrealized Losses	0	253	392
12 Months or More, Fair Value	19,651	34,707	14,693
12 Months or More, Gross Unrealized Losses	349	286	307
Total, Fair Value	19,651	39,454	44,291
Total, Gross Unrealized Losses	349	539	699
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	6,040	5,725	4,675
12 Months or More, Gross Unrealized Losses	4,460	4,775	5,825
Total, Fair Value	6,040	5,725	4,675
Total, Gross Unrealized Losses	$ 4,460	$ 4,775	$ 5,825