Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	$ 20,829	$ 25,527
Less than 12 Months Fair Value	544,201	437,414
Less than 12 Months Unrealized Losses	(3,917)	(2,350)
12 Months or More Fair Value	352,912	561,668
12 Months or More Unrealized Losses	(9,870)	(11,989)
Total Fair Value	897,113	999,082
Total Unrealized Losses	(13,787)	(14,339)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	13,787	14,339
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	8,427	10,219
Less than 12 Months Fair Value	290,497	258,825
Less than 12 Months Unrealized Losses	(2,468)	(1,287)
12 Months or More Fair Value	200,514	279,015
12 Months or More Unrealized Losses	(7,014)	(6,924)
Total Fair Value	491,011	537,840
Total Unrealized Losses	(9,482)	(8,211)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	9,482	8,210
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	11,184	14,432
Less than 12 Months Fair Value	123,367	71,026
Less than 12 Months Unrealized Losses	(1,020)	(543)
12 Months or More Fair Value	29,701	44,148
12 Months or More Unrealized Losses	(980)	(982)
Total Fair Value	153,068	115,174
Total Unrealized Losses	(2,000)	(1,525)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2,000	1,526
US Government Corporations and Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	1,195	856
Less than 12 Months Fair Value	128,033	105,250
Less than 12 Months Unrealized Losses	(418)	(518)
12 Months or More Fair Value	100,277	216,221
12 Months or More Unrealized Losses	(1,466)	(3,551)
Total Fair Value	228,310	321,471
Total Unrealized Losses	(1,884)	(4,069)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1,884	4,069
US Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	0	0
Less than 12 Months Fair Value	0	0
Less than 12 Months Unrealized Losses	0	0
12 Months or More Fair Value	19,613	19,450
12 Months or More Unrealized Losses	(262)	(411)
Total Fair Value	19,613	19,450
Total Unrealized Losses	(262)	(411)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	262	411
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	23	20
Less than 12 Months Fair Value	2,304	2,313
Less than 12 Months Unrealized Losses	(11)	(2)
12 Months or More Fair Value	2,807	2,834
12 Months or More Unrealized Losses	(148)	(121)
Total Fair Value	5,111	5,147
Total Unrealized Losses	(159)	(123)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 159	$ 123