Investment Securities (Summary of Investment Securities with Gross Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	$ 449,480	$ 548,723	$ 205,142
Less Than 12 Months, Gross Unrealized Losses	9,409	13,007	2,013
12 Months or More, Fair Value	105,584	73,865	45,310
12 Months or More, Gross Unrealized Losses	6,773	5,491	5,068
Total, Fair Value	555,064	622,588	250,452
Total, Gross Unrealized Losses	16,182	18,498	7,081
Government sponsored agencies [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	45,396	47,352	17,281
Less Than 12 Months, Gross Unrealized Losses	110	205	168
12 Months or More, Fair Value	15,204	14,031	0
12 Months or More, Gross Unrealized Losses	188	177	0
Total, Fair Value	60,600	61,383	17,281
Total, Gross Unrealized Losses	298	382	168
State and political subdivisions [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	79,787	126,345	73,880
Less Than 12 Months, Gross Unrealized Losses	4,942	6,475	1,667
12 Months or More, Fair Value	56,180	19,074	10,685
12 Months or More, Gross Unrealized Losses	2,041	378	219
Total, Fair Value	135,967	145,419	84,565
Total, Gross Unrealized Losses	6,983	6,853	1,886
Residential mortgage-backed securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	247,397	274,076	86,179
Less Than 12 Months, Gross Unrealized Losses	3,472	5,097	45
12 Months or More, Fair Value	0	0	374
12 Months or More, Gross Unrealized Losses	0	0	3
Total, Fair Value	247,397	274,076	86,553
Total, Gross Unrealized Losses	3,472	5,097	48
Collateralized Mortgage Obligations [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	76,900	84,995	27,802
Less Than 12 Months, Gross Unrealized Losses	885	1,127	133
12 Months or More, Fair Value	12,833	14,684	8,560
12 Months or More, Gross Unrealized Losses	411	512	37
Total, Fair Value	89,733	99,679	36,362
Total, Gross Unrealized Losses	1,296	1,639	170
Corporate bonds [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	0	14,931	0
Less Than 12 Months, Gross Unrealized Losses	0	78	0
12 Months or More, Fair Value	14,907	19,826	19,651
12 Months or More, Gross Unrealized Losses	93	174	349
Total, Fair Value	14,907	34,757	19,651
Total, Gross Unrealized Losses	93	252	349
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	6,460	6,250	6,040
12 Months or More, Gross Unrealized Losses	4,040	4,250	4,460
Total, Fair Value	6,460	6,250	6,040
Total, Gross Unrealized Losses	4,040	4,250	4,460
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