Investment Securities (Summary of Investment Securities with Gross Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	$ 176,747	$ 548,723	$ 570,518
Less Than 12 Months, Gross Unrealized Losses	4,243	13,007	12,375
12 Months or More, Fair Value	341,437	73,865	86,785
12 Months or More, Gross Unrealized Losses	9,746	5,491	6,609
Total, Fair Value	518,184	622,588	657,303
Total, Gross Unrealized Losses	13,989	18,498	18,984
Government sponsored agencies [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	1,744	47,352	43,816
Less Than 12 Months, Gross Unrealized Losses	4	205	223
12 Months or More, Fair Value	24,810	14,031	14,395
12 Months or More, Gross Unrealized Losses	38	177	181
Total, Fair Value	26,554	61,383	58,211
Total, Gross Unrealized Losses	42	382	404
State and political subdivisions [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	91,532	126,345	120,232
Less Than 12 Months, Gross Unrealized Losses	4,010	6,475	6,918
12 Months or More, Fair Value	70,116	19,074	30,915
12 Months or More, Gross Unrealized Losses	2,466	378	1,528
Total, Fair Value	161,648	145,419	151,147
Total, Gross Unrealized Losses	6,476	6,853	8,446
Residential mortgage-backed securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	34,280	274,076	267,495
Less Than 12 Months, Gross Unrealized Losses	144	5,097	3,532
12 Months or More, Fair Value	196,045	0	40
12 Months or More, Gross Unrealized Losses	2,571	0	2
Total, Fair Value	230,325	274,076	267,535
Total, Gross Unrealized Losses	2,715	5,097	3,534
Collateralized Mortgage Obligations [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	44,195	84,995	129,049
Less Than 12 Months, Gross Unrealized Losses	81	1,127	1,617
12 Months or More, Fair Value	28,544	14,684	15,302
12 Months or More, Gross Unrealized Losses	1,093	512	531
Total, Fair Value	72,739	99,679	144,351
Total, Gross Unrealized Losses	1,174	1,639	2,148
Corporate bonds [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	4,996	14,931	9,926
Less Than 12 Months, Gross Unrealized Losses	4	78	85
12 Months or More, Fair Value	14,937	19,826	19,883
12 Months or More, Gross Unrealized Losses	63	174	117
Total, Fair Value	19,933	34,757	29,809
Total, Gross Unrealized Losses	67	252	202
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	6,985	6,250	6,250
12 Months or More, Gross Unrealized Losses	3,515	4,250	4,250
Total, Fair Value	6,985	6,250	6,250
Total, Gross Unrealized Losses	3,515	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