Investment Securities (Summary of Investment Securities with Gross Unrealized Losses) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	$ 97,602	$ 554,907	$ 530,665
Less Than 12 Months, Gross Unrealized Losses	270	5,945	7,392
12 Months or More, Fair Value	72,676	133,159	146,094
12 Months or More, Gross Unrealized Losses	1,062	3,140	3,687
Total, Fair Value	170,278	688,066	676,759
Total, Gross Unrealized Losses	1,332	9,085	11,079
Government sponsored agencies [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	14,110	114,640	24,789
Less Than 12 Months, Gross Unrealized Losses	19	292	163
12 Months or More, Fair Value	18,787	21,681	14,715
12 Months or More, Gross Unrealized Losses	517	508	37
Total, Fair Value	32,897	136,321	39,504
Total, Gross Unrealized Losses	536	800	200
State and political subdivisions [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	73,532	195,285	258,503
Less Than 12 Months, Gross Unrealized Losses	237	2,891	5,433
12 Months or More, Fair Value	25,713	68,361	63,584
12 Months or More, Gross Unrealized Losses	84	1,627	2,493
Total, Fair Value	99,245	263,646	322,087
Total, Gross Unrealized Losses	321	4,518	7,926
Residential mortgage-backed securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value		169,226	187,858
Less Than 12 Months, Gross Unrealized Losses		2,146	1,592
12 Months or More, Fair Value		3,435	3,643
12 Months or More, Gross Unrealized Losses		76	102
Total, Fair Value		172,661	191,501
Total, Gross Unrealized Losses		2,222	1,694
Collateralized Mortgage Obligations [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	8,461	60,459	49,845
Less Than 12 Months, Gross Unrealized Losses	13	408	155
12 Months or More, Fair Value	22,955	39,382	48,881
12 Months or More, Gross Unrealized Losses	182	729	826
Total, Fair Value	31,416	99,841	98,726
Total, Gross Unrealized Losses	195	1,137	981
Corporate bonds [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	0	9,532	9,670
Less Than 12 Months, Gross Unrealized Losses	0	200	49
12 Months or More, Fair Value	4,936	0	14,971
12 Months or More, Gross Unrealized Losses	64	0	29
Total, Fair Value	4,936	9,532	24,641
Total, Gross Unrealized Losses	64	200	78
Trust Preferred Securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value	1,499	0	0
Less Than 12 Months, Gross Unrealized Losses	1	0	0
12 Months or More, Fair Value	285	300	300
12 Months or More, Gross Unrealized Losses	215	200	200
Total, Fair Value	1,784	300	300
Total, Gross Unrealized Losses	$ 216	200	$ 200
US Treasury Securities [Member]
Summary of continuous unrealized loss position of securities
Less Than 12 Months, Fair Value		5,765
Less Than 12 Months, Gross Unrealized Losses		8
12 Months or More, Fair Value		0
12 Months or More, Gross Unrealized Losses		0
Total, Fair Value		5,765
Total, Gross Unrealized Losses		$ 8