Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	$ 31,790	$ 25,527
Less than 12 Months Fair Value	142,162	437,414
Less than 12 Months Unrealized Losses	(863)	(2,350)
12 Months or More Fair Value	445,231	561,668
12 Months or More Unrealized Losses	(5,745)	(11,989)
Total Fair Value	587,393	999,082
Total Unrealized Losses	(6,608)	(14,339)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	6,608	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	13,765	10,219
Less than 12 Months Fair Value	94,304	258,825
Less than 12 Months Unrealized Losses	(634)	(1,287)
12 Months or More Fair Value	213,050	279,015
12 Months or More Unrealized Losses	(4,007)	(6,924)
Total Fair Value	307,354	537,840
Total Unrealized Losses	(4,641)	(8,211)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4,641	8,210
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	15,434	14,432
Less than 12 Months Fair Value	45,809	71,026
Less than 12 Months Unrealized Losses	(227)	(543)
12 Months or More Fair Value	31,597	44,148
12 Months or More Unrealized Losses	(505)	(982)
Total Fair Value	77,406	115,174
Total Unrealized Losses	(732)	(1,525)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	732	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	2,551	856
Less than 12 Months Fair Value	999	105,250
Less than 12 Months Unrealized Losses	(1)	(518)
12 Months or More Fair Value	178,013	216,221
12 Months or More Unrealized Losses	(982)	(3,551)
Total Fair Value	179,012	321,471
Total Unrealized Losses	(983)	(4,069)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	983	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	1,050	0
Less than 12 Months Unrealized Losses	(1)	0
12 Months or More Fair Value	19,728	19,450
12 Months or More Unrealized Losses	(139)	(411)
Total Fair Value	20,778	19,450
Total Unrealized Losses	(140)	(411)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	140	411
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities Gross Unrealized Gain, instant	40	20
Less than 12 Months Fair Value	0	2,313
Less than 12 Months Unrealized Losses	0	(2)
12 Months or More Fair Value	2,843	2,834
12 Months or More Unrealized Losses	(112)	(121)
Total Fair Value	2,843	5,147
Total Unrealized Losses	(112)	(123)
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 112	$ 123