Investment Securities (Summary of Investment Securities with Gross Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	$ 156,938	$ 548,723	$ 559,269
Less Than 12 Months, Gross Unrealized Losses	4,182	13,007	10,393
12 Months or More, Fair Value	370,668	73,865	53,844
12 Months or More, Gross Unrealized Losses	8,646	5,491	4,892
Total, Fair Value	527,606	622,588	613,113
Total, Gross Unrealized Losses	12,828	18,498	15,285
Government sponsored agencies [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	2,377	47,352	58,646
Less Than 12 Months, Gross Unrealized Losses	2	205	400
12 Months or More, Fair Value	44,786	14,031	0
12 Months or More, Gross Unrealized Losses	139	177	0
Total, Fair Value	47,163	61,383	58,646
Total, Gross Unrealized Losses	141	382	400
State and political subdivisions [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	92,279	126,345	128,062
Less Than 12 Months, Gross Unrealized Losses	4,047	6,475	4,707
12 Months or More, Fair Value	71,421	19,074	19,378
12 Months or More, Gross Unrealized Losses	2,282	378	482
Total, Fair Value	163,700	145,419	147,440
Total, Gross Unrealized Losses	6,329	6,853	5,189
Residential mortgage-backed securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	10,144	274,076	267,211
Less Than 12 Months, Gross Unrealized Losses	60	5,097	4,217
12 Months or More, Fair Value	197,042	0	257
12 Months or More, Gross Unrealized Losses	1,362	0	2
Total, Fair Value	207,186	274,076	267,468
Total, Gross Unrealized Losses	1,422	5,097	4,219
Collateralized Mortgage Obligations [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	47,142	84,995	100,469
Less Than 12 Months, Gross Unrealized Losses	68	1,127	939
12 Months or More, Fair Value	35,722	14,684	8,083
12 Months or More, Gross Unrealized Losses	1,060	512	34
Total, Fair Value	82,864	99,679	108,552
Total, Gross Unrealized Losses	1,128	1,639	973
Corporate bonds [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	4,996	14,931	4,881
Less Than 12 Months, Gross Unrealized Losses	5	78	130
12 Months or More, Fair Value	14,922	19,826	19,876
12 Months or More, Gross Unrealized Losses	78	174	124
Total, Fair Value	19,918	34,757	24,757
Total, Gross Unrealized Losses	83	252	254
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	6,775	6,250	6,250
12 Months or More, Gross Unrealized Losses	3,725	4,250	4,250
Total, Fair Value	6,775	6,250	6,250
Total, Gross Unrealized Losses	3,725	4,250	4,250
Preferred Stock [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value		1,024
Less Than 12 Months, Gross Unrealized Losses		25
12 Months or More, Fair Value		0
12 Months or More, Gross Unrealized Losses		0
Total, Fair Value		1,024
Total, Gross Unrealized Losses		$ 25